Power transmission apparatus

ABSTRACT

A power transmission apparatus manipulates the transmission of power of the mechanical and/or electrical form. The power transmission apparatus is constructed integrating together a power-transmitting device and a transmission interaction redistributing mechanism. The interaction redistributing mechanism redistributes, or remaps, an optimized section of the operating speed range of the power-transmitting device onto the full operating speed range, including the stall speed, of the power transmission apparatus. Full operating speed range, including low speeds, is optimized. In a mechanical implementation of the apparatus, an epicyclic gear train is utilized as the redistributing mechanism. In an electromagnetic implementation of the apparatus, a rotary commutator is utilized as the redistributing mechanism and the power-transmitting device is an electromagnetic device. The mechanical implementation is capable of handling mechanical-to-mechanical mode of power transmission. Various versions of the electromagnetic implementation are capable of handling either the mechanical-to-mechanical, electrical-to-mechanical, mechanical-to-electrical, electrical-to-electrical mode, or more than one of the four modes, of power transmission. Both the mechanical and the electromagnetic implementations are capable of power regeneration.

BACKGROUND

1. Field of the Invention

This invention relates in general to an apparatus for manipulating thetransmission of power. In particular, this invention relates to anapparatus for optimized transmission of mechanical or electrical powerproduced by a power source to a load, with the transmitted powerfulfilling the specific mechanical or electrical power requirementwithin the full operating speed range of the load.

2. Technical Background

Power is a measure to rate the flow of energy, or work done, per unittime. Electrical power has been conveniently available in households, infactories, and, for example, in the overhead power line system ofelectrified railway for various applications. On the other hand,mechanical power that is provided as raw motive power by prime moverssuch as internal combustion engines consuming fossil fuel is alsoconvenient. In practical applications, these are the two forms ofreadily-available power source in modern society.

The term "power" is used herein as a general term to designate eitherthe mechanical or the electrical form of power. For the discussion ofthe invention, "power transmission" thus broadly refers to thetransmission of mechanical or electrical power to either mechanical orelectrical power. Relevant forms of power concerning the manipulation ofpower transmission as performed by the apparatus of the invention thusinclude mechanical and electrical power.

When both mechanical and electrical forms of power are considered, therecan be four possible modes of power transmission. In conventionalterminology, the transmission of mechanical power to mechanical isgenerally referred as mechanical power transmission, as is in vehiculardrive train applications. The transmission of electrical power tomechanical, when utilizing an electric motor, is referred to as electricmotoring. In contrast, the transmission of mechanical power toelectrical, when employing an electric generator, is electrical powergeneration. Electrical-to-electrical power transmission generallyinvolves the regulation of voltage and/or frequency of the electricalpower. In the extreme case of zero frequency of the AC electrical power,it becomes the DC electrical power.

The need for power transmission is based on one simple reason. Namely,the sources providing the power, either mechanical or electrical, arefrequently operating to generate the power at conditions not directlydesirable at the load that is consuming the power. Generally, thecharacteristic factors of power source and load concerned include, inthe mechanical power, torque and speed and, in the electrical power,frequency and voltage. For both forms of power, efficiency is a factorof ever increasing importance. For example, considering the vast numberof internal combustion engine-driven vehicles used world-wide, smallimprovements in vehicle power plant and transmission efficiencies can betranslated into the huge conservation of petroleum consumption. Incritical applications such as electric vehicle, the bottleneck ofstorage battery technology turns the efficiency of electric drive systeminto one of the most important design factors.

An internal combustion engine needs a transmission box to provide thetorque-speed regulation in order to meet propulsion demands at thevehicle driving wheels. Conventional vehicle internal combustion enginedoes not provide stall torque, while every vehicle has to be acceleratedfrom standstill. This means that an internal combustion engine whichoperates within a limited speed range--not including stall speed--mustdrive the load in a full operating speed range--including the stallspeed. The transmission box in an automobile is used to perform thistransmission of mechanical power along with the necessary torque/speedregulations. But traditional automobile transmissions built aroundmultiple-speed-geared torque converters suffer drawbacks. They requirethe use of precision fluid logic valve mechanism to switch the torqueconverter among the three or more sets of gear train of different gearratios. The multiple sets of gear trains installed in a typicaltransmission box, in which only one is functional at any given time, addto the overall weight of the system, and the torque converter operateswith poor efficiency at low speeds.

An electric machine operating in the motoring mode--commonly known asthe electric motor--does provide stall torque, but with poor efficiency.In large-power electric motor drives, poor starting-speed efficiencyimposes heat dissipation problem that the drives must reduce their powerrating at low operating speeds in order to prevent permanent damagescaused by overheating. Though power electronics devices such as PWM(pulse-width modulation) systems do expand operating speed range andimprove motor drive efficiencies, they are generally sophisticated andcostly to build.

An electric machine operating in the generating mode as an electricgenerator is also constrained by input mechanical speed ranges. Forexample, a wind turbine driving an electric generator has a limitationof minimum wind speed. Below that minimum, the generator system isdifficult, if not impossible, to generate an AC power that can beacceptable for house or industrial application.

Thus, when considered as machines for the transmission of the mechanicaland/or electrical power in the generalized sense, conventional drivesystems, either vehicle transmissions, electric motor drives orgenerators, all suffer from the low-efficiency performancecharacteristics at low operating speeds. Yet low-speed operation is asituation inevitable for practically all such power drives. In somesituations such as vehicle transmissions operating in traffic congestionconditions, this poor-efficiency performance at low speeds deterioratesair pollution problem at a large scale considering the number ofvehicles caught in the traffic. Most of these conventional powertransmission machines, though optimized for a fraction, frequently atthe high-speed end, of their respective full operating speed range, cannot cover the full speed range with optimized performance. Electricmotor drives employing digital-controlled power electronics systems canindeed improve overall performance than simple motors in their designedoperating speed ranges. However, power electronics motor control systemsare sophisticated and expensive to build.

For the foregoing reasons, there is a need for a power transmissionapparatus that can transmit power within its full operating speed rangewith optimized performance characteristics.

SUMMARY

The invention is directed to a power transmission apparatus fortransmitting power at optimized efficiencies within the full operatingspeed range. A power transmission apparatus having features of theinvention comprises a power-transmitting means and a power transmissioninteraction redistributing means. The power-transmitting means comprisesa first transmission interaction element and a second transmissioninteraction element and is connected to the input of the apparatus forreceiving an external power at an input angular speed. The first and thesecond transmission interaction elements operate at a first and a secondangular speed respectively for transmitting power via interactionbetween the two. The transmission interaction redistributing means isintegrated with the power-transmitting means and the output of theapparatus. The power-transmitting interaction of the power-transmittingmeans operating at the first and the second angular speeds isredistributed onto the output by the transmission interactionredistributing means, and the output delivers the power to an externalload at an output angular speed.

In a mechanical implementation of the invention, a power transmissionapparatus having features of the invention comprises apower-transmitting means and an epicyclic gear train. Thepower-transmitting means comprises a driving element and a drivenelement and is connected to the input shaft of the apparatus forreceiving an external mechanical power at an input angular speed. Thedriving and the driven elements of the power-transmitting means operateat a driving and a driven angular speed respectively for transmittingthe mechanical power via interaction between the driving and the drivenelements. The epicyclic gear train comprises a first, a second and athird gear, the second gear rotates in the same rotational direction asthe third gear and at an angular speed slower than the third gear whenthe third gear is driven while the first gear is held stationary. Thethird gear is connected to the driving element of the power-transmittingmeans, the second gear is connected to the driven element of thepower-transmitting means, and the first gear is connected to the outputshaft of the apparatus. The power-transmitting interaction of thepower-transmitting means operating at the driving and the driven angularspeeds is redistributed onto the output shaft of the apparatus by theepicyclic gear train, and the output shaft delivers the mechanical powerto the external load at an output angular speed.

In an electromagnetic implementation of the invention, a powertransmission apparatus having features of the invention comprises anelectromagnetic power-transmitting means and a rotary commutator. Theelectromagnetic power-transmitting means comprises a firstelectromagnetic element and a second electromagnetic element. Theelectromagnetic power-transmitting means receives the external power atan input angular speed, and the first and second electromagneticelements operate at a first and a second angular speed respectively fortransmitting power via electromagnetic interaction between the magneticfields established by the first and second electromagnetic elementsrespectively. The rotary commutator magnetizes the first electromagneticelement and is integrated with the first and second electromagneticelements of the electromagnetic power-transmitting means. The rotarycommutator operates at a commutation angular speed to magnetize thefirst electromagnetic element and establishes in the firstelectromagnetic element a first rotating magnetic field rotating at anangular speed that is synchronous with the angular speed of a secondrotating magnetic field established by the second electromagneticelement. The power-transmitting electromagnetic interaction of theelectromagnetic power-transmitting means operating at the synchronizedangular speed of the first and second rotating magnetic fields isredistributed onto the output of the apparatus by the rotary commutator,and the output delivers the power from the electromagneticpower-transmitting means to the external load at an output angularspeed.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of the invention willbecome better understood with regard to the following description,appended claims, and accompanying drawings where:

FIG. 1 schematically illustrates a generalized power transmissionapparatus of the invention;

FIG. 2 shows the relationship between the normalized angular speed andthe effective gear ratio of a power-transmitting device;

FIG. 3 shows the relationship between the normalized angular speed andthe effective gear ratio of a generalized power transmission apparatusof FIG. 1;

FIG. 4 shows the relationship between the normalized angular speed andthe effective gear ratio of the generalized power transmission apparatusof FIG. 1 having a different configurational arrangement;

FIGS. 5, 6 and 7 respectively illustrate the angular speed relationshipsof the gear elements in a standard planetary, all-spur planetary anddifferential gear trains when utilized as a transmission interactionredistributing mechanism for constructing a mechanical implementation ofthe power transmission apparatus of FIG. 1

FIGS. 8, 9 and 10 respectively illustrate the angular speedrelationships of the gear elements in a standard planetary, all-spurplanetary and differential gear trains when utilized as a transmissioninteraction redistributing mechanism for constructing anotherarrangement of the mechanical implementation of the power transmissionapparatus of FIG. 1;

FIG. 11 outlines the structural configuration of a generalizedmechanical implementation of the power transmission apparatus of theinvention;

FIG. 12 illustrates in a perspective view an embodiment of a mechanicalimplementation of the power transmission apparatus of FIG. 11 adopting acoaxial configuration;

FIG. 13 illustrates another embodiment of the mechanical implementationof the power transmission apparatus of FIG. 11 adopting a parallel-axisconfiguration;

FIG. 14 is a perspective view of an embodiment of the mechanicalimplementation of the power transmission apparatus of FIG. 11 in which avariable-pitch cone-pulley drive is utilized as the power-transmittingdevice;

FIG. 15 illustrates the angular speed/gear ratio diagram for aparallel-axis arrangement of the mechanical implementation of FIG. 13having different gearing ratios for the two couplings integrating thepower-transmitting means and the interaction redistributing means;

FIG. 16 illustrates the angular speed/gear ratio diagram for anotherparallel-axis arrangement of the mechanical implementation of FIG. 13having different gear ratios for the two couplings integrating thepower-transmitting means and the interaction redistributing means;

FIG. 17 schematically illustrates an equilibrium lever system in aplanetary gear train, in which the power-transmitting device of themechanical implementation of FIG. 13 receives the mechanical motivepower for output via the sun gear;

FIG. 18 schematically illustrates the equilibrium lever system in aplanetary gear train, in which the power-transmitting device of themechanical implementation of FIG. 13 is operated in the reverseddirection of power flow as compared to the situation of FIG. 17;

FIG. 19 illustrates a cross-sectional view of a mechanicalimplementation of the power transmission apparatus of the inventionutilizing an induction machine as the power-transmitting device;

FIG. 20 illustrates the equivalent angular speed/gear ratio diagram forthe elements of the power-transmitting device and the interactionredistributing mechanism of an electromagnetic implementation of thepower transmission apparatus of the invention;

FIG. 21 illustrates a generalized electromagnetic implementation of thepower transmission apparatus of FIG. 1;

FIG. 22 illustrates a cross-sectional view of an embodiment of thegeneralized electromagnetic implementation of FIG. 21 in which theelectromagnetic assembly is a poly-phase winding and themagnetization-redistributing electromagnetic winding assembly is an ACarmature;

FIG. 23 illustrates the cross-sectional view of an embodiment of thegeneralized electromagnetic implementation of FIG. 21 in which theelectromagnetic assembly is a poly-phase winding and themagnetization-redistributing electromagnetic winding assembly is a DCarmature;

FIG. 24 illustrates the cross-sectional view of an embodiment of thegeneralized electromagnetic implementation of FIG. 21 in which theelectromagnetic assembly is an electromagnet winding and themagnetization-redistributing electromagnetic winding assembly is an ACarmature;

FIG. 25 illustrates the cross-sectional view of an embodiment of thegeneralized electromagnetic implementation of FIG. 21 in which theelectromagnetic assembly is an electromagnet winding and themagnetization-redistributing electromagnetic winding assembly is a DCarmature;

FIG. 26 illustrates the cross-sectional view of an embodiment of thegeneralized electromagnetic implementation of FIG. 21 in which theelectromagnetic assembly is a permanent magnet assembly and themagnetization-redistributing electromagnetic winding assembly is an ACarmature;

FIG. 27 illustrates the cross-sectional view of an embodiment of thegeneralized electromagnetic implementation of FIG. 21 in which theelectromagnetic assembly is a permanent magnet assembly and themagnetization-redistributing electromagnetic winding assembly is a DCarmature;

FIG. 28 illustrates the structural configuration of a mechanical rotarycommutator suitable for incorporation into the electromagneticimplementation of the power transmission apparatus of the invention;

FIG. 29 is a schematic diagram showing the circuitry configuration of apower electronics rotary commutator suitable for incorporation into theelectromagnetic implementation of the power transmission apparatus ofthe invention; and

FIG. 30 illustrates the electrical system of an electromagneticimplementation of the power transmission apparatus of the inventionutilized as the regenerative traction drive for electrified railwayapplication.

DESCRIPTION

The best modes of implementation of the power transmission apparatus ofthe invention will be described in the following paragraphs. Before thevarious embodiments of the invention are described in detail, however,several general issues require clarification and definition.

A power transmission apparatus of the invention has an input and anoutput. When a power transmission apparatus of the invention performspower transmission, its input receives power from an external powersource, and its output delivers power to an external load. The apparatusof the invention is suitable for the transmission of power in ageneralized sense as the term power transmission is concerned.Mechanical and electrical forms of power are applicable. In variousembodiments of the invention, either mechanical or electrical power canbe input from the external power source to the power transmissionapparatus, which may output either mechanical or electrical power to theexternal load.

In most of the embodiments of the invention to be exemplified below, thepower transmission apparatus of the invention is also capable ofperforming the transmission of power, either mechanical or electrical,in the reversed direction of power flow. In other words, in addition tothe normal operation of transmitting power from the input to the outputof the apparatus, there can be occasions in which the same apparatus canbe operated in the reversed direction of power flow, thus permittingpower regeneration by the system making use of the power transmissionapparatus. For example, in an electrical-to-mechanical powertransmission apparatus of the invention that is integrated in the drivetrain of the traction system of an electric locomotive, the ability toperform the reverse-direction power transmission enables the locomotiveto implement regenerative braking.

Further, for the purpose of describing the invention, when electricalpower is concerned, a DC electrical power is considered to be a specialcase of a poly-phase AC electrical power. In other words, a DCelectrical power is considered to be a single-phase AC with zerofrequency. It is in effect an AC power that never changes the polarityof its electric potential.

The Generalized Power Transmission Apparatus

A power transmission apparatus in accordance with the invention isconstructed by integrating a power-transmitting device with atransmission interaction redistributing mechanism. For the constructionof the power transmission apparatus of the invention, the fundamentalconcept of the use of the redistributing mechanism and its integrationwith the power-transmitting device is two-fold. First, thepower-transmitting interaction of the functional elements of thepower-transmitting device employed to construct the apparatus isredistributed. Second, redistribution of the power-transmittinginteraction achieves to constrain the operation of thepower-transmitting device within its optimized performance range. Theredistribution of the constrained operating speed range of thepower-transmitting device allows the output of the apparatus to cover afull operating speed range including the stall speed.

FIG. 1 schematically illustrates a generalized power transmissionapparatus of the invention. Essentially, the apparatus 100 is comprisedof a power-transmitting means 110 and a power transmission interactionredistributing means 120. In the drawings, note that for similarembodiments of the power transmission apparatus of invention to bedescribed below, the same reference numeral is used to designate likeelements or elements with equivalent functionality, although suchequivalent elements may differ greatly in construction.

In general, the power-transmitting means 110 is comprised of at leasttwo power transmission interaction elements 111 and 112, in which afirst element transmits power to a second for implementing itsinteraction of power transmission. The power transmitted inside thepower-transmitting means 110 is received from an external power source181 via an input 131 of the apparatus. The power-transmitting means 110is integrated with the transmission interaction redistributing means 120to make up the power transmission apparatus. The power received by thepower-transmitting means 110 from the external power source 181 is thenredistributed by the transmission interaction redistributing means 120onto an output 132 of the apparatus and delivered to an external load182.

The power transmission apparatus 100 of FIG. 1 is capable of handlingmechanical and electrical power. When the power received by theapparatus is mechanical power, the input 131 of the apparatus is arotary shaft that can be mechanically coupled to the external powersource 181. In this case, the external power source 181 is a mechanicalpower source that generates motive power, and the input coupling 171 isa mechanical coupling. When the power received by the apparatus is anelectrical power, the input 131 of the apparatus is an electrical leadthat can be electrically connected to the external power source 181. Inthis case, the external power source 181 is an electrical power sourcethat generates an electrical power, and the input coupling 171 is anelectrical coupling.

At the output end of the apparatus, when the power delivered by theapparatus is a mechanical power, the output 132 of the apparatus is arotary shaft that can be mechanically coupled to the external load 182.In this case, the external load 182 is a mechanical load that consumesmechanical motive power, and the output coupling 172 is a mechanicalcoupling. When the power delivered by the apparatus is an electricalpower, the output 132 of the apparatus is an electrical lead that can beelectrically connected to the external load 182. In this case, theexternal load 182 is an electrical load that consumes electrical power,and the output coupling 172 is an electrical coupling.

Internal to the power transmission apparatus, the integration betweenthe elements of the power-transmitting means 110 and the elements of thepower transmission interaction redistributing means 120 is schematicallyoutlined in the drawing by a number of, for example, two couplings 141and 142 in the depicted drawing. These couplings, depending on thespecific type of implementation of the apparatus, may be eithermechanical or electrical couplings.

When seeking the practical usefulness of the very fundamental concept ofthe invention, feasible implementations of the concept can be generallycategorized into two groups. Based on the principle of operationinternal to the power transmission apparatuses constructed, mechanicaland electromagnetic implementations of the invention are possible. Amechanical implementation of the power transmission apparatus is onethat the power transmission as performed by the power-transmitting meansand interacting onto the output of the apparatus is redistributed by theinteraction redistributing means via mechanical interaction. Incontrast, an electromagnetic implementation of the apparatus is one thatthe power transmission is redistributed via electromagnetic interaction.

Both implementations incorporate the use of a power transmissioninteraction redistributing mechanism. For the electromagneticimplementation, the power-transmitting means used to constructed theapparatus of the invention must be an electric machine based onelectromagnetism, though the electric machine used may be varied instructural details from the traditional ones widely used nowadays. Theelectromagnetic interaction in the power-transmitting means isintegrated with that of the interaction redistributing means tofacilitate the functionality of the power transmission apparatus of theinvention.

On the other hand, the power-transmitting means used to construct theapparatus of the invention in a mechanical implementation may be allsorts of power-transmitting devices though, again, their structuraldetails may be varied from their traditional counterparts. Themechanical power-transmitting interaction is redistributed integrallywith the mechanical interaction of the redistributing means onto theoutput shaft of the apparatus via the mechanical interaction of force.Power-transmitting devices suitable for constructing a mechanicalimplementation of the apparatus of the invention may include electricmachines, which are operated as simple mechanical power-transmittingdevices, similar in functionality as in the case in which a hydraulictorque converter is used as the power-transmitting device.

The mechanical implementation of the power transmission apparatus of theinvention is suitable for the mechanical-to-mechanical powertransmission. Various types of the power transmission apparatus of theelectromagnetic implementation may be utilized in themechanical-to-mechanical, electrical-to-mechanical,mechanical-to-electrical, and electrical-to-electrical modes of powertransmission respectively.

Mechanical power-transmitting devices suitable for constructing thepower transmission apparatus of the invention can be varied. Many of theindustry-proven mechanical power-transmitting devices or their modifiedvariants can be applicable. They include, for example, hydraulic devicessuch as fluid coupler and torque converter, electromagnetic devices suchas eddy-current clutch, motor-generator set and induction machine withpermanent magnet field element, and so on. Modified versions of theseconventional mechanical power-transmitting devices can be used. Forexample, a conventional torque converter can be modified so that itsoptimized operating characteristics, efficiency namely, is emphasized atits high-speed end in order to be particularly suitable for applicationin the power transmission apparatus of the invention. Though itslow-speed performance would become even poorer due to the emphasis onhigh-speed performance, but a power transmission apparatus of theinvention constructed utilizing such a modified torque converter doesnot require the torque converter to operate in this poor-performancelow-speed range. On the other hand, electromagnetic power-transmittingdevices suitable for constructing the power transmission apparatus ofthe invention are basically electric machines that performelectromagnetic motoring and generating based on the principle ofelectromagnetism. Many of the existing versions of electric machine suchas AC induction machine, DC motor/generator, or their respectivemodified versions are applicable.

Before proceeding to elaborate into the fundamental concept ofinteraction redistribution of the invention, refer to FIG. 2 of thedrawing. FIG. 2 is a diagram showing the relationship between thenormalized angular speed and the gear ratio of a power-transmittingdevice. In the coordinate system, the axis of abscissae, the x-axis,represents the effective gear ratio of the power-transmitting device,and the axis of ordinates, the y-axis, represents the normalized angularspeed of the constituent elements of the device that are rotary ineither the mechanical or electrical sense. The effective gear ratio of apower-transmitting device is defined to be the ratio obtained bydividing the angular speed of the output to that of the input of thedevice. On the other hand, the normalized angular speed of any of thefunctional elements of the power-transmitting device is defined to bethe ratio of the angular speeds obtained by dividing the angular speedof the specific element by a predetermined reference angular speed.

Thus, for the impeller of a torque converter, this normalized angularspeed may be the ratio obtained by dividing the impeller angular speedby a selected reference angular speed of the internal combustion enginedriving the torque converter. The reference angular speed of theinternal combustion engine selected may be one at its rated poweroutput, for example. If the engine drives the impeller of the torqueconverter directly, this normalized angular speed for the impellerbecomes one, a case of unity normalized angular speed. On the otherhand, the normalized angular speed of the turbine of this torqueconverter measured at the same reference angular speed is always lessthan unity. In the case of the rotor of an AC electric machine, thisnormalized angular speed is the ratio obtained by dividing the angularspeed of the rotor shaft by that converted from the frequency of thefeeding AC power source. The line frequency is normally 60 or 50 hertz(Hz) in most utility networks.

Note that the power transmission apparatus of the invention is itself apower-transmitting device whose characteristics can be described in thediagram of FIG. 2 as well. Thus, assuming that an external power sourceis delivering power to the input of the power-transmitting device at afixed 100 percent, or unity, rated angular speed as represented by ahorizontal input speed line 101, then the output of the device can beplotted in the coordinate system against the gear ratio over the axis ofabscissae as a variable. The angular speed of the output can berepresented by an output speed line 102 as a function of the device gearratio. Thus, for example, at a gear ratio of 0.5, the output operates at50 percent of the input speed, as is represented by the point 105 on theoutput speed line 102. Note that gear ratio can be greater than unitywhen the output operates at angular speeds faster than input, or it canbe a negative number when the output rotates in the reverse directionwith respect to the input.

In the conventional power-transmitting devices utilized as a mechanicalpower transmission system, it is frequently required that the drivenelement which functions as the output of the system be operative in afull speed range. To be practical for applications such as vehiclepropulsion, the full speed range is usually required to include thestall speed, i.e, a speed of gear ratio zero in the speed/gear ratiodiagram of FIG. 2. Thus, in the case of an automotive transmission basedon the hydraulic torque converter, the converter turbine speed rangemust be stretched down to the stall point for the vehicle to start fromstandstill. Unfortunately, for a torque converter, low turbine speedsrepresent low energy efficiencies as is well known in the field.

Each of the power-transmitting devices that can be used to construct thepower transmission apparatus of the invention has a driving and a drivenelement. When operating, the driving element propels the driven elementvia the transmission interaction between the two. In the mechanicalimplementation of the invention, the power-transmitting device may beone that relies on mechanical friction to operate as is in the case of ahydraulic torque converter or, it may also be one that operates underthe principle of electromagnetic coupling as is in the case of aninduction machine. In the electromagnetic implementation of theinvention, the power-transmitting device may be some type of electricmachine operating under the principle of electric motoring andgenerating. Whatever the case, the power-transmitting device isintegrated with a transmission interaction redistributing mechanism sothat redistribution of the power-transmitting interaction providesimproved power transmission characteristics unique to the apparatus ofthe invention.

When incorporated into an apparatus of the invention, apower-transmitting device may be operated only in a selected smallsection of its own full operating speed range while permitting theoutput of the apparatus to cover a full operating speed range, includingthe stall speed. This small speed section can be selected to avoid thelow-speed range that includes the stall speed where the performance ofthe power-transmitting device itself in terms of efficiency is poor. Thepower transmission apparatus of the invention employs a powertransmission interaction redistributing mechanism to achieve this in amanner to be described below.

FIG. 3 is a diagram showing the relationship between the normalizedangular speed and the effective gear ratio of the generalized powertransmission apparatus of FIG. 1. As is with FIG. 2, the axis ofabscissae represents the effective gear ratio, and the axis of ordinatesrepresents the angular speed of the functional elements of theapparatus. An input speed line 101 represents the input speed of thepower transmission apparatus, assuming that the external power source181 is providing power to the input 131 of the apparatus at a fixed 100percent rated angular speed. Output 132 of the apparatus is required tocover the full operating speed range including the stall speed as isrepresented by an output speed line 102. A reasonable and practical fullspeed range may include the line section from point A to B along theoutput speed line 102, corresponding to a gear ratio range of from zeroto unity on the x-axis.

In the generalized power transmission apparatus of FIG. 1, depending onthe input configurational arrangement for the apparatus, the apparatusinput 131 may either be connected to the driving element 111 or thedriven element 112 of the power-transmitting device 110. In onemechanical implementation of the power transmission apparatus of FIG. 1,assume a power-transmitting device 110 has its driving element 111connected to the input 131 of the apparatus. The driving element 111receives the input power at the fixed speed along the horizontal speedline 101 of FIG. 3, and its driven element 112 driven to operate atspeeds identified by a driven element speed line 103. The output speedline 102 in FIG. 3 represents the angular speed of the output shaft 132of the apparatus.

Thus, with simultaneous reference to FIGS. 1 and 3, for the output 132of the mechanical implementation of the apparatus to operate in a fullspeed range from zero to unity gear ratio as represented by the linesection of points A and B on the output speed line 102, the drivenelement 112 of the power-transmitting device 110 has to operatecorrespondingly in its operating speed range of the line section frompoint C to B on the driven element speed line 103. The output speedrange of the apparatus from point A to B on the output speed line 102 isa full output speed range of zero to 100 percent of the input speedapplied to input 131. Corresponding to this full output speed range, thedriven element 112 of the power-transmitting device 110 only has tooperate in a small speed range of from, for example, about 75 to 100percent of the speed of the driving element 111. To achieve this, thepower transmission interaction redistributing mechanism 120 isintegrated with the power-transmitting device 110 to implement thisspeed range redistribution, or, remapping for that matter.

FIG. 4 illustrates the angular speed/gear ratio diagram of themechanical implementation of the generalized power transmissionapparatus of FIG. 1 employing a different configurational arrangementfor the input of the apparatus. Unlike in the case of FIG. 3 in whichthe driving element 111 of the power-transmitting device 110 isconnected to the apparatus input 131, in the arrangement of FIG. 4, thedriving element 111 of device 110 is not directly connected to theapparatus input 131. Instead, the apparatus input 13 1 in thearrangement of FIG. 4 is connected to the driven element 112. In thiscase, speed line 103 of the driven element 112 now represents the inputspeed line of the apparatus. The concept of redistribution of a smallsection of the operating speed range of the power-transmitting device110 onto the full speed range of the apparatus 100 is the same as isdescribed for the arrangement of FIG. 3, except that the driven element112 is maintained at fixed operating speed while the driving element 111changes speed as the effective gear ratio of the apparatus changes.

By contrast, in the case of the electromagnetic implementation, theapparatus input 131 is always the driving element of the electromagneticpower-transmitting device 110 incorporated in the apparatus. In anelectromagnetic implementation of the generalized power transmissionapparatus of FIG. 1, an electromagnetic power-transmitting device 110 ofthe electric machine type has its driving and the driven elements 111and 112 operating at the same angular speed regardless of the effectivegear ratio of the apparatus output. Thus, in the case of theelectromagnetic implementation of the apparatus, the concept ofredistribution of the transmission interaction becomes redistributing,instead of a small range, a fixed operating speed of thepower-transmitting device 110 onto the full speed range of the apparatus100. Similar as in the mechanical implementation, this fixed operatingspeed for the power-transmitting device 110 of the electromagneticimplementation can be optimally selected.

For example, the driving element of an electromagneticpower-transmitting device may be the field element of an electricmachine that generates a rotating magnetic field. The driven elementmay, on the other hand, be an armature that is amagnetization-redistributing electromagnetic winding assembly generatinganother magnetic field rotating at the same angular speed as that of thedriving element. In this case, in the diagram of FIG. 3, the drivenelement speed line 103 becomes superimposed on the input speed line 101.In other words, speed line 101 now represents the angular speed of boththe driving 111 and the driven element 112 of the electromagneticpower-transmitting device 110 employed to construct the apparatus of theinvention. Output speed line 102 still represents the angular speed ofthe apparatus output 132, and the line 103 is non-existent in the caseof the electromagnetic implementation. In this case, the diagram of FIG.3 effectively reduces to that of FIG. 2 which is more suitable fordescribing the electromagnetic implementation of the apparatus of theinvention.

For the electromagnetic implementation of the apparatus of theinvention, the respective magnetic fields of the driving and the drivenelements must be synchronized, just as is in the case of a conventionalAC synchronous motor. In an AC synchronous motor, the permanent magnetrotor or its electromagnet equivalent must be rotating synchronous tothe rotating magnetic field generated by the field winding. Out ofsynchronization between the two leads to lock-up of the motor. Bycontrast, in the mechanical implementation of the power transmissionapparatus of the invention, there must be a slip between the driving andthe driven elements of the power-transmitting device such as is in ahydraulic torque converter. The driven element does not reach to 100percent the speed of the driving element.

Note that in the case of an apparatus of the invention that involves thetransmission of electrical power, the axis of ordinates in FIGS. 2 and 3represents the ratio of frequencies of the AC electrical power, eitherinput or output. The effective gear ratio, the ratio between thefrequencies of the AC output and input power, is represented by the axisof abscissae.

The Mechanical Implementation of the Apparatus

Thus, the generalized power transmission apparatus of the invention asdepicted in FIG. 1 is capable of delivering good performance at thelow-speed end of its entire output operating speed range. For example,in the case of a mechanical implementation that performsmechanical-to-mechanical power transmission or, an electromagneticimplementation that performs electrical-to-mechanical powertransmission, both of which finds application in vehicle drive trains,good low-speed performance means that the drive train complexity can bereduced while enjoying improved low-speed efficiencies. The followingparagraphs describe the embodiments of these mechanical andelectromagnetic implementations of the power transmission apparatus ofthe invention.

A mechanical implementation of the power transmission apparatus of theinvention is defined to be one that incorporates a power-transmittingdevice and a mechanical transmission interaction redistributingmechanism. The two constituent parts are integrated together in themanner according to the invention so as to form an apparatus that isoperated as a mechanical-to-mechanical power transmission system. Themechanical transmission interaction redistributing mechanism may be asimple epicyclic gear train. This epicyclic gear train may either be thestandard planetary gear train having a ring gear, the all-spur planetarygear train without a ring gear, or the differential gear train. For thepurpose of facilitating the mechanical redistribution of the powertransmission interaction, these gear trains are considered to be andreferred to herein as epicyclic gear trains.

As a mechanical transmission interaction redistributing mechanism, thestandard planetary gear train is one that incorporates a set of piniongears held by a framework of a carrier, which allows both the ring andsun gears to rotate with respect to the carrier gear. In the same sense,the all-spur planetary gear train is one that incorporates a set ofdouble-pinion gears held by a carrier that allows both the small andlarge sun gears to rotate with respect to the carrier gear. Similarly,the differential gear train is one that incorporates a set of piniongears held by a carrier that allows both its bevel gears to rotate withrespect to the carrier gear. In the following descriptions, the pinioncarrier is referred to as the carrier gear.

One distinguished and essential characteristics of the mechanicalimplementation of the power transmission apparatus of the invention isthat all gears and the pinion carrier of the epicyclic gear trainutilized as the interaction redistributing means rotate when theapparatus operates to transmit power. Though the standard planetary, theall-spur planetary and the differential gear trains appear to bestructurally different, they are topologically equivalent. For thepurpose of functioning as the redistributing means in the apparatus ofthe invention, with its pinion gears, the carrier gear of the gear trainpermits the other two gears, be it the ring and sun gears in thestandard planetary, the small and large sun gears in the all-spurplanetary or the side bevels in the differential, to mesh with thepinion gears so as to rotate at speeds and directions determined by thegear train geometry.

FIGS. 5, 6 and 7 respectively illustrate the angular speed relationshipsof the gear elements in the standard planetary, all-spur planetary anddifferential gear trains when each of the gear trains is utilized as atransmission interaction redistributing mechanism for constructing amechanical implementation of the power transmission apparatus of theinvention. In FIGS. 5, 6 and 7, the axis of abscissae represents theoutput-to-input gear ratio of the power transmission apparatus, and theaxis of ordinates represents the normalized angular speed of the gearsin the gear trains.

The speed relationships of the gear elements in the gear trains of FIGS.5, 6 and 7 may be expressed as the motion equations of the epicyclicgear trains which may be derived from the gear sizes and the topologicalconfigurations of the respective gear trains. For example, in the caseof a standard planetary gear train of FIG. 5, assuming the ring gear hasa radius R and the sun gear a radius S. If the ring gear angular speedis maintained at the normalized unity speed as illustrated by the inputspeed line 101 in FIG. 5 and the sun gear is allowed to vary its speedlinearly against the x-axis along the output speed line 102 from gearratio zero at point A to unity at point B, then the angular speed of thesun gear in the y-axis is simply ω_(S) =x, where the variable xrepresents the gear ratio. In this case, the angular speed of thecarrier gear ω_(C) =represented by the speed line 103 may be determinedby the equation ω_(C) =(Sx+R)/(R+S). When the sun gear is at stall speedof point A, the speed of the carrier gear at point C is R/(R+S). At theopposite end, when the sun gear is brought up to the speed of the ringgear at point B, the carrier gear rotates at the same speed as the ringand sun gears. In fact, the three gears rotate at the same angular speedat the unity gear ratio of point B.

For the other two types of epicyclic gear trains, there exists similarspeed relationships. For example, for the all-spur planetary gear trainof FIG. 6, assuming the large sun gear has a radius S_(L) and the smallsun gear a radius of S_(S). If the carrier gear angular speed ismaintained at the normalized unity speed on the input speed line 101while the small sun gear varies its speed linearly against the x-axisalong output speed line 102 from gear ratio zero of point A to unity ofpoint B, then the angular speed of the small sun gear in the y-axis issimply ω_(S).sbsb.S =x. The angular speed of the large sun gear may bedetermined by the equation ω_(S).sbsb.L =(S_(S) ² X+S_(L) ² -S_(S)²)/S_(L) ² as represented by the speed line 103. When the sun gear is atstall speed on point A, the speed of the large sun gear on point C is(S_(L) ² -S_(S) ²)/S_(L) ².

For the differential gear train with both bevel gears symmetrically thesame size as characterized in FIG. 7, if the angular speed of one of thebevel gears is maintained at the normalized unity speed on the inputspeed line 101, while the other bevel gear is allowed to vary from gearratio zero on point A to unity on point B along output speed line 102,then the angular speed of this output bevel gear in the y-axis is simplyω_(B).sbsb.1 =x. The angular speed of the carrier gear w_(C) may bedetermined by the equation ω_(C) =(x+1)/2 along the speed line 103. Whenthe output bevel gear is at stall speed on point A, the speed of thecarrier gear is half that of the first bevel gear on point C.

FIG. 11 illustrates a generalized mechanical implementation of the powertransmission apparatus of the invention in an elevational view. Theapparatus 200 is comprised of a mechanical power-transmitting means 210and an epicyclic gear train 220 that is utilized as the mechanicaltransmission interaction redistributing means. Note that FIG. 11 doesnot show the structural details of the integration between the elementsof the power-transmitting means 210 and the gear elements of theepicyclic gear train 220. Rather, the integration is illustratedschematically only to show the interrelationship between elements of thetwo constituent means 210 and 220. Details of structural integration aredependent on the configurational dimensions of the elements of bothmeans 210 and 220 and are readily comprehensible when specificintegration requirements between the two are outlined.

In general, the mechanical power-transmitting means 210 is comprised ofat least two transmission interaction elements 211 and 212. One of thetwo elements is the driving element that operates at a driving angularspeed and transmits the mechanical power to the other, which is thedriven element that operates at a driven angular speed. The interactionbetween the driving and the driven elements 211 and 212 facilitates thepower transmission of the mechanical power-transmitting means 210.

The mechanical power transmitted internal to the mechanicalpower-transmitting means 210 is received from an external mechanicalpower source via an input rotary shaft 231 of the apparatus. Themechanical power-transmitting means 210 is integrated with themechanical transmission interaction redistributing means 220 to make upthe mechanical power transmission apparatus. The mechanical powerreceived by the mechanical power-transmitting means 210 from theexternal mechanical power source is then redistributed by the mechanicaltransmission interaction redistributing means 220 onto an output rotaryshaft 232 of the apparatus and delivered to an external mechanical load.

The mechanical transmission interaction redistribution means 220 is anepicyclic gear train comprising a first gear 221, a second gear 222 anda third gear 223. The second gear 222 of the epicyclic gear trainrotates in the same rotational direction as the third gear 223 and at anangular speed slower than the third gear when the third gear is drivenwith the first gear 221 held stationary. This angular speed relationshipbetween the gear elements of the epicyclic gear train 220 is illustratedin all the angular speed/gear ratio diagrams of FIGS. 5-7 and 8-10,which demonstrate the relationship for different gear trains withdifferent input arrangements. The gear ratio range between points A andB in each of drawings of FIGS. 5-7 and 8-10 satisfies this requirementif angular speed of the first, the second and the third gear followspeed line 102, 103 and 101 respectively.

To integrate the mechanical power-transmitting means 210 and theepicyclic gear train 220 together in order to construct a mechanicalimplementation of the power transmission apparatus of the invention, thethird gear 223 of the epicyclic gear train is connected to the drivingelement 211 of the mechanical power-transmitting means, the second gear222 is connected to the driven element 212 of the mechanicalpower-transmitting means, and the first gear 221 is connected to theoutput rotary shaft 232 of the apparatus.

In the drawing of FIG. 11, the driven element 212 of thepower-transmitting means 210 is connected to the second, the carriergear 222, of the epicyclic gear train 220 by a coupling means 242. Onthe other hand, the driving element 211 is connected to the third, thering gear 223, of the gear train 220 by a coupling means 241. Since thestructure of both the power-transmitting means 210 and the epicyclicgear train 220 are symmetrical with respect to the longitudinal axis ofthe apparatus along the axial center line of the input and output rotaryshafts 231 and 232, these two direct coupling means 241 and 242 maylikewise be made axially symmetrical. However, other than the directcoupling as illustrated in the drawing, other coupling means such asgearing or belt traction are also allowed as will be described in detailin the following paragraphs.

The power-transmitting interaction of the driving element 211 and drivenelement 212 of the mechanical power-transmitting means 210 operating atthe driving and the driven angular speeds respectively is redistributedonto the output rotary shaft 232 by the epicyclic gear train 220, andthe output rotary shaft 232 delivers the mechanical power to theexternal mechanical load at an output angular speed.

As described above, the standard planetary, all-spur planetary anddifferential gear trains are considered to be epicyclic gear trains solong as they are utilized as the mechanical transmission interactionredistributing means. Thus, the epicyclic gear train 220 in theembodiment of the mechanical implementation of the apparatus of FIG. 11can either be the standard planetary, the all-spur planetary, or thedifferential gear train.

Due to the topological characteristics of the various types of epicyclicgear trains applicable for constructing the mechanical implementation ofthe apparatus of the invention, the integration of the elements of theredistributing means with that of the power-transmitting means can beimplemented in different configurational arrangements. However, allthese varied arrangements of integration of the two must comply with theprinciple of the invention, although the performance characteristics ofthe apparatus would be altered slightly. Though, note that all theapplicable integration arrangements must satisfy the condition for speedrelationship among the gear elements of the gear train as describedabove. Specifically, in the gear train used as the interactionredistributing means for the apparatus, the second gear rotates in thesame rotational direction as the third gear and at an angular speedslower than the third gear when the third gear is driven with the firstgear held stationary.

Thus, a standard planetary gear train used as the transmissioninteraction redistributing means comprises a sun gear, a carrier gearcarrying a suitable number of pinion gears and a ring gear. In onearrangement of the mechanical implementation of the power transmissionapparatus of the invention as illustrated in FIG. 11, the first gear 221of the standard planetary gear train that serves as the output shaft 232of the power transmission apparatus is the sun gear. The second gear 222that is connected to the driven element 212 of the power-transmittingmeans 210 is the carrier gear, and the third gear 223 connected to thedriving element 211 is the ring gear. In an alternative arrangement, thefirst gear 221 that serves as the output 232 of the apparatus of theinvention is the ring gear. The second gear 222 that is connected to thedriven element 212 of the power-transmitting means 210 is the carriergear, and the third gear 223 connected to the driving element 211 is thesun gear.

Similarly, in the case of an all-spur planetary gear train, in onearrangement, the first gear 221 of the gear train 220 that serves as theoutput shaft 232 of the apparatus of the invention is the small sungear. The second gear 222 that is connected to the driven element 212 ofthe power-transmitting means 210 is the large sun gear, and the thirdgear 223 connected to the driving element 211 is the carrier gear. In analternative arrangement, the first gear 221 that serves as the output232 of the apparatus of the invention is the carrier gear. The secondgear 222 that is connected to the driven element 212 of thepower-transmitting means 210 is the large sun gear, and the third gear223 connected to the driving element 211 is the small sun gear.

When a differential gear train is used as the interaction redistributingmeans 220 in FIG. 11, it is comprised of a pair of bevel gears and acarrier gear carrying a suitable number of pinion gears. In the case ofa symmetrical differential gear train, i.e., the sizes of the two bevelsare the same, there is only one effective integration arrangement. Thefirst gear 221 of the differential gear train 220 that serves as theoutput 232 of the apparatus of the invention is one of the two bevelgears. The second gear 222 that is connected to the driven element 212of the power-transmitting means 210 is the carrier gear, and the thirdgear 223 connected to the driving element 211 is the other of the twobevel gears.

When apparatus performance characteristics is concerned, the substantialdifference between the two integration arrangements for each of thethree types of epicyclic gear trains described above rests on thedimensional configuration of the gears in the respective gear train. Inother words, the relative sizes of the ring and sun gears of thestandard planetary and the small and large sun gears of the all-spurplanetary gear trains respectively determine the performancecharacteristics of the power transmission apparatus constructed.

When constructing a mechanical implementation of the power transmissionapparatus of the invention as generally outlined in FIG. 11, thestructural integration of the power-transmitting means 210 and thetransmission interaction redistributing means 220 can be either directlycoaxial or offset at parallel axes. For the coaxial arrangement, theinput and output shafts 231 and 232 of the apparatus can be aligned onthe same axis, and the entire apparatus can be constructed in arelatively compact package. On the other hand, the parallel-axisarrangement is suitable for those power-transmitting devices such asvariable-pitch cone-pulley drives having noncoaxial input and outputshafts. Parallel-axis arrangement is also suitable for those apparatusof the invention requiring special final gear ratio adjustments, as willbe described in the following paragraphs. FIGS. 12 and 13 respectivelydepict the coaxial and parallel-axis structural arrangementsrespectively.

FIG. 12 illustrates an embodiment of a mechanical implementation of thepower transmission apparatus of FIG. 11 that adopts the coaxialconfiguration. In the perspective view of the depicted apparatus, apower-transmission device 210 such as a fluid coupler and a standardplanetary gear train 220 are utilized as the power-transmitting meansand the transmission interaction redistributing means respectively. Notethat the drawing does not show details of the gear teeth of the gearelements, nor does it show the various bearings used to support theelements in place and provide for adequate lubricated rotation. On thespatial relationship between the elements of device 210 and gear train220 is demonstrated.

In this coaxial arrangement, the central axes of symmetry of both means210 and 220 coincide with each other, and are further aligned with theinput shaft 231 and the output shaft 232 of the apparatus. The drivingelement, the impeller 211, of the fluid coupler 210 is directly fixed tothe ring gear 223 of the gear train 220 via a coupling framework 241.The driven element, the turbine 212, is directly fixed to the carrier222 of the gear train 220 that holds pinion gears 224 in position. Thecarrier 222 is fixed to the driven element 212 via a coupling shaft 242.The carrier 222 is not made in the form of a gear as there is no suchrequirement for it to be engaged with any other gear in this describedexample. Thus, in this coaxial arrangement, the impeller 211 of thefluid coupler 210 rotates in synchronous with the ring gear 223 of theplanetary gear train 220, and the turbine 212 synchronous with thecarrier 222.

FIG. 13 illustrates another embodiment of the generalized mechanicalimplementation of the power transmission of FIG. 11 adopting theparallel-axis configurational arrangement. The mechanical implementationof FIG. 13 utilizes the same power-transmitting means and thetransmission interaction redistributing means as those of the apparatusof FIG. 12. In the perspective view, again, gearing teeth and supportbearings are not detailed. In this parallel-axis arrangement, theimpeller 211 and the turbine 212 of the fluid coupler 210 may be coupledto the ring gear 223 and the carrier gear 222 of the planetary geartrain 220 via suitable mechanical couplings respectively. Though notshown in the drawing, the mechanical couplings may, for example, be viagear teeth formed on the circumferential surface of the respectiveelements so that adequate gear meshing can be made between the twocoupled pairs. If the spatial conditions require, an idler gear ofsuitable size can be arranged between each of the coupled pairs. Oralternatively, belt drives can be used to provide the necessarymechanical coupling for the two pairs.

FIG. 14 is a perspective view of another embodiment of the mechanicalimplementation of the power transmission apparatus of FIG. 11 in which avariable-pitch cone-pulley drive 210 operating on a traction belt 213 isutilized as the power-transmitting means. Due to the spatialconfiguration of such a belt drive, the driven element of thepower-transmitting means, i.e. the driven pulley 212, must be installedon a shaft 242 parallel and offset to the shaft 241 of the drivingelement, i.e., the driving pulley 211. The driving pulley 211 is coupleddirectly to the ring gear 223 of the planetary gear train 220 via theshaft 241. The driven pulley 212 is coupled to the carrier gear 222 ofthe planetary 220 via another belt drive 240 utilizing a belt 243. Forsimplicity, this second belt drive 240 may be a fixed-pitch oneemploying pulleys 245 and 246. Pulley 246 is directly connected to thecarrier gear 222 of the gear train 220. Instead of this second beltdrive 240, an idler gear may be used to provide the equivalentmechanical coupling in an alternative arrangement. Note that themechanism responsible for varying the pitch of the driving pulley 211and/or driven pulley 212 are not shown in the drawing.

In the embodiment of either FIG. 12, 13 or 14, adequate housing to theapparatus depending on the particular application can be provided toprotect the entire power transmission system. Further, the epicyclicgear train used as the interaction redistributing mechanism may need anenclosing housing to maintain proper lubrication for its gears.

In the non-coaxial, i.e. the parallel-axis configuration of FIG. 13,when gearing is utilized to provide the two necessary mechanicalcoupling between the elements of the power-transmitting device 210 andthat of the transmission interaction redistributing mechanism 220, eachof the gear ratios for both coupled pairs need not be unity, and the twogear ratios need not be the same. This also applies to the parallel-axisarrangement such as is in the case of FIG. 14 in which belt coupling isused. In belt couplings, the pitch ratios of the two pulleys are treatedas gear ratios herein. The difference between the gear ratios for thetwo couplings can be employed as a factor for adjusting the finalgearing ratio of the power transmission apparatus of the invention. FIG.15 illustrates the angular speed/gear ratio diagram for such anarrangement. For example, in the parallel-axis arrangement of FIG. 13,in which a fluid coupler or torque converter is utilized as thepower-transmitting means 210, the driven element 212 of thepower-transmitting means 210 is coupled to the second gear 222 of theepicyclic gear train 220 at a gear ratio smaller than that of thecoupling between the driving element 211 and the third gear 223.

In the case of the parallel-axis apparatus of FIG. 13 depicting theconfigurational arrangement of FIG. 15, assume that the fluid couplerimpeller 211 is coupled to the ring gear 223 of the planetary gear train220 at a unity gear ratio along input speed line 101 in order that bothrotates at the same angular speed. Meanwhile, the turbine 212 is coupledto the carrier gear 222 at a gear ratio of 3/2 so that the turbineangular speed is two-thirds that of the carrier gear 222. It is furtherassumed that the planetary gear train 220 has a ring-to-sun gear ratioof 3/1. This arrangement permits the output shaft 232 of the powertransmission apparatus at the sun gear 221 of the planetary 220 to reachto an angular speed equivalent to a final gear ratio of nearly threealong the output speed line 102. This means, as the power-transmittingfluid coupler 210 operates in an accelerating process from an equivalentgearing ratio of 50 percent at point C to nearly 100 percent at point Dalong the speed line 103_(A) which is 2/3gear-reduced with respect tospeed line 103, the output shaft 232 of the apparatus operates in acorresponding speed range of zero at point A to three times the speed ofthe input shaft 231 at point B along the output speed line 102. This isequivalent to a final gear ratio of three for the power transmissionapparatus.

In contrast to the configurational arrangement of FIG. 15, consider thesituation of the apparatus of FIG. 13 as depicted in FIG. 16. Let thefluid coupler turbine 212 be coupled to the carrier gear 222 of theplanetary 220 at a unity gear ratio in order that both rotates at thesame angular speed. On the other hand, the impeller 211 is coupled tothe ring gear 223 at a gear ratio of 8/7 so that the impeller angularspeed is seven-eighths (0.875) that of the ring gear 223 along the speedline 101_(A), which is 7/8 gear-reduced with respect to that of theinput speed line 101. Again, assume that the planetary gear train 220has a ring-to-sun gear ratio of 3/1. This system may allow the outputshaft 232 of the apparatus at the sun gear 221 to reach to an angularspeed equivalent to a final gear ratio of only nearly 0.5. Thus, as thefluid coupler 210 speeds up from the equivalent gear ratio of 85.7percent (0.75/0.875) at point C to nearly 100 percent at point D alongthe speed line 103, the output shaft 232 of the apparatus operates in acorresponding speed range of zero at point A to one half the speed ofthe input shaft 231 at point B along the output speed line 102, anequivalent final gear ratio of 0.5 for the power transmission apparatus.

Thus, the configurational arrangements of employing different couplinggear ratio for the elements of the power-transmitting and theinteraction redistributing means as described in FIGS. 15 and 16respectively are functionally equivalent to the use of a final gearadjustment stage for the apparatus of the invention that employs thecoaxial arrangement. Though the parallel-axis arrangement is relativelymore complex in structure than the coaxial, it enjoys the advantage ofeasy final gear ratio adjustment without the need for an additionalgearing stage if the application of the apparatus has its output speedrange not compatible to that of the input.

For a mechanical implementation of the power transmission apparatus ofthe invention constructed out of the integration of a power-transmittingdevice and an epicyclic gear train, note that either the driving or thedriven element of the power-transmitting device may serve as the inputof the apparatus to receive mechanical motive power from the externalpower source. The difference between the use of either the driving orthe driven element of the mechanical power-transmitting device as theapparatus input is the slight mutual deviation between the apparatusperformance characteristics in both cases. This becomes obvious if theangular speed relationships of gear elements of the epicyclic geartrains as illustrated in FIGS. 5, 6 and 7 are compared with those shownin FIGS. 8, 9 and 10 respectively. The slight difference is a result ofthe sustaining of the comparison basis that the input shaft be kept atconstant angular speed.

In the cases of FIGS. 5, 6 and 7 respectively representing the use ofthe standard planetary, the all-spur planetary and the differential geartrain as the power transmission interaction redistributing mechanism,the third gear of each of the epicyclic gear trains is connected to thedriving element of the power-transmitting device. Thus the third gear ofeach of the epicyclic gear trains serves as the input of the apparatusfor receiving the external mechanical motive power, as is represented bythe input speed line 101 in FIGS. 5, 6 and 7. In contrast, for the casesof FIGS. 8, 9 and 10 respectively, it is the second gear of each of theepicyclic gear train which is connected to the driven element of thepower-transmitting device that serves as the input of the apparatus, asis represented by the input speed line 103. A comparison of each of thethree types of epicyclic gear trains reveals the fact that thepower-transmitting device operates under different driving and drivenelement angular speeds in each of its two configurational arrangementssuch that the apparatus performance characteristics become shifted.

Note that when referring to the first, the second and the third gears ofthe epicyclic gear trains, there must be the satisfied condition thatthe second gear of the epicyclic gear train rotates in the samerotational direction as the third gear and at an angular speed slowerthan the third gear when the third gear is driven with the first gearheld stationary. The six configurational arrangements for thegeneralized mechanical implementation of the apparatus of FIG. 11 asdepicted in FIGS. 5-7 and FIGS. 8-10 are two groups of arrangement forthe three types of epicyclic gear trains complying to this speedrelationship requirement. There are another two groups of arrangementfor the three types of epicyclic gear trains also complying to the veryspeed relationship requirement.

The first group is correspondent to the arrangement of FIGS. 5-7 and maybe obtained by swapping the gear elements represented by speed lines 101and 102 in each of the three arrangements. The second group iscorrespondent to the arrangement of FIGS. 8-10 and may also be obtainedby swapping the gear elements represented by speed lines 101 and 102 ineach of the three arrangements. For example, the ring gear representedby speed line 101 and the sun gear represented by speed line 102 of bothFIG. 5 and 8 may be swapped so that speed line 101 becomes representingthe sun gear and speed line 102 the ring gear. In each of the swappedarrangements, the speed equation for the gear represented by speed line103 is also altered accordingly by shifting its point C on the axis ofordinates.

Consider the mechanical implementation of the power transmissionapparatus outlined in FIG. 12 again. Assuming again that thepower-transmitting device 210 is a fluid coupler and the transmissioninteraction redistributing mechanism 220 a planetary gear train. Theangular speed relationships among the various rotary elements of thisapparatus can be described in the diagram of FIG. 5. In its structuralintegration arrangement, the driving element, impeller 211, of the fluidcoupler 210 is connected to the ring gear 223, and the driven, turbine212, to the carrier gear 222. Sun gear 221 of the gear train 220functions as the output shaft 232 of the power transmission apparatus.Mechanical input from the external power source can be applied to eitherthe driving 211 or the driven element 212 or, either the ring 223 or thecarrier gear 222 respectively. In other words, either the driving or thedriven element of the power-transmitting device can serve as the inputof the power transmission apparatus.

From the angular speed/gear ratio relationship of FIG. 5, it is clearthat when the ring gear 223 is maintained at unity angular speed, forthe sun gear 221 (i.e., the output 232 of the power transmissionapparatus) to operate in a speed range of zero to unity gear ratio, thecarrier gear 222 needs only to vary its angular speed from R/(R+S) tounity gear ratio. In a typical planetary gear train with the sun gearhaving a radius one-third that of the ring gear, this is a range from 75(i.e., 3/(3+1)) to 100 percent of the ring gear speed. In other words,as the driving element 211 of the power-transmitting device 210 isdriving at unity angular speed, the driven element 212 only needs tooperate from 75 to 100% the speed of the driving element 211 so that theoutput 232 of the apparatus can deliver a full speed range of zero to100 percent of the input angular speed received at the apparatus input231. In a sense, the 75-to-100 percent speed range--not including thestall speed--of the power-transmitting device 210, a fluid coupler, isredistributed, or remapped for that matter, to the full speed range ofthe apparatus--including the stall speed.

For apparatuses of the invention employing power-transmitting deviceswhose driven element can not outrun the driving element in speed whentransmitting power, normally the apparatus can only operate within thegear ratio range between zero and unity to transmit mechanical powerfrom its input to output shaft. This assumes that the couplings betweenthe driving and driven element of the power-transmitting device andtheir corresponding gear elements in the epicyclic gear train are at thesame gear ratio. This is because, in these power-transmitting devices,mechanical motive power is only transmitted from the element operatingat greater speed to the other at slower speed.

Within this gear ratio range, the configurational arrangement for theapparatus is capable of receiving mechanical power at its inputshaft--either the driving element of the power-transmitting device orthe driven element, and delivering mechanical power at its output shaft,thereby facilitating the transmission of mechanical power. In the gearratio range from zero to unity, the entire power transmission apparatushas a natural tendency of accelerating its mechanically loaded outputshaft from stall to unity gear ratio speed. This happens as the inputshaft is receiving mechanical power from the external power source andallowing the driving element of the power-transmitting device, theimpeller of a fluid coupler for example, to bring up the speed of thedriven element, turbine, together with its load. The tendency is towardthe direction in the diagram of FIG. 5 with less slip between thedriving and driven elements of the power-transmitting device.Specifically, this is the direction from point A to B along the outputspeed line 102 in FIG. 5.

In those apparatuses of the invention employing other power-transmittingdevices such as the variable-pitch cone-pulley drive, the equivalentgear ratio range of the apparatus is not limited to the range of fromzero to unity gear ratio. Gear ratio of the power-transmitting deviceitself, among others, constitutes one of the parameters for determiningthe effective gear ratio of the power transmission apparatus. If thepower-transmitting device does provide a gear ratio in which its drivingelement is operating at an angular speed slower than the driven element,then the equivalent gear ratio of the apparatus can then exceed unity,as is clearly shown in the diagrams depicted in FIGS. 5-7 and 8-10.

In fact, in the power-transmitting device such as a fluid coupler whosetwo interaction elements are substantially symmetrical, the one that isdriving at a faster angular speed is referred to as the impeller, andthe other that is driven at the slower speed is referred to as theturbine. There are occasions in which the situation is reversed, inwhich the impeller becomes the turbine and the turbine becomes theimpeller by definition simply because the speed relationship isreversed. This permits the reversed direction of power flow as comparedto that when the apparatus is operating in the normal direction of powerflow.

For example, consider again the apparatus of FIG. 12 with a fluidcoupler used as the power-transmitting device 210 and a planetary geartrain as the transmission interaction redistributing mechanism 220. Andagain, one hydraulic blade element 211 of the fluid coupler 210 isconnected to the ring gear 223, and the other 212 to the carrier gear222. When the external mechanical power source is input to the apparatusat, for example, the element 211 of the fluid coupler that is connectedto the ring gear 223, the apparatus transmits mechanical power to theoutput shaft 232 at the sun gear 221.

Assume that the power source, an internal combustion engine for example,driving the apparatus input 231 along the input speed line 101 hasbrought the angular speed of the output shaft 232 up to a point E alongthe output speed line 102 at the high-speed end of FIG. 5 within thegear ratio range from zero to unity. Further assume that the powersource then reduces its angular speed to a level of reduced engine speedline 101_(R) on the y-axis below the angular speed level of the currentspeed of the sun gear 221 on point E. In this case, the output speedpoint E in the original coordinate system of FIG. 5 representing theoriginal status of the apparatus becomes a point beyond the unity gearratio in a reduced-scale coordinate system, whose unity gear ratio isidentified by the point B_(R) along the common output speed line 102.

Under such situation, angular speed of the ring gear 223 connecting tothe blade element 211 that was originally the driving impeller elementhas come down to the point F on the reduced engine speed line 101_(R).Angular speed of the blade element 211 at this point F is slower thanthe corresponding angular speed at point G along the reduced carrierspeed line 103_(R) of the carrier gear 222 connecting to the bladeelement 212 that was originally the driven turbine element. In thiscase, the roles of the two hydraulic blades 211 and 212 in the fluidcoupler 210 are exchanged. The one blade 211 that was originally theimpeller now becomes the turbine since it is now driven at the slowerspeed by the other blade 212 that was originally the turbine, which nowbecomes the impeller as it is driving the other at a faster angularspeed. Thus, the mechanical power flows in the reversed direction, withthe sun gear 221 of the planetary 220 being the input, and the ring gear223 becomes the output. For applications such as in a vehicle drivetrain, this is a situation known as engine braking. With suitableenergy-harnessing arrangements such as those found in hybrid andelectric vehicles, this may provide the vehicle with the capability ofregenerative braking.

Within the planetary gear train used as the transmission interactionredistributing mechanism, each of the pinion gears with its respectivecentral axis pivoting on the suitable bearing arrangement of the carriergear must establish a balanced lever system with the sun and ring gearsgear-meshed at the opposite ends of the pivot center point. FIG. 17schematically illustrates such an equilibrium lever system in aplanetary gear train in which the power-transmitting device such as afluid coupler is receiving the mechanical motive power for output viathe sun gear of the apparatus.

As is shown in the drawing, an imaginary lever 225 identified by phantomline and formed of one of the pinion gears 224 is gear-meshed with thering gear 223 and sun gear 221 at the opposite ends of the lever 225.Assuming that the external power source delivers the mechanical motivepower to the apparatus via the driving element 211 fixed to the ringgear 223 of the planetary gear train 220 in the clockwise direction asobserved in the drawing. The driven element 212 of thepower-transmitting device that is fixed to the carrier gear 222 isdriven to rotate also in the clockwise direction. The carrier gear 222thus drives the imaginary lever 225, i.e., the entire pinion gear 224,to move in the clockwise direction. Since the pinion gear 224 is alsorotating with respect to the framework of the carrier gear 222 when theentire system operates, a bearing schematically identified by thereference numeral 226 provides for the adequate lubricated rotationalsupport.

The lever 225, with its outer end gear-meshed with the ring gear 223 toprovide the counter force, permits the mechanical motive power receivedfrom the external power source by the power-transmitting device to betransmitted to the sun gear 221 via the gear-meshing at its inner end.Thus, the sun gear 221 is driven to rotate along the clockwise directionand delivers the received power to the external load of the apparatus.

With reference to the angular speed/gear ratio diagram of FIG. 5, it canbe observed that in this balanced lever system of FIG. 17, the apparatusis thus capable of redistributing the mechanical power received at theangular speed of either the driving or the driven element of thepower-transmitting device onto the output shaft at the angular speed ofthe sun gear. Phenomenally, the gear meshing point between the piniongear 224 and the sun gear 221 travels over the circumferential surfaceof the sun gear 221 at the angular speed of the carrier gear 222 of thegear train, while the sun gear 221 itself is rotating at its own angularspeed different from the carrier gear 222.

FIG. 18 schematically outlines the balanced lever system in a planetarygear train in case that the power-transmitting device is operated in thereversed direction as compared to the situation of FIG. 17. For all-spurplanetary and differential gear trains, similar situations exist as allthese epicyclic gear trains are topologically equivalent when theirstructural configurations are concerned. Although planetary gear trainis used to explain the lever balancing, the above reasoning isapplicable to all types of epicyclic gear trains, including theplanetary, all-spur planetary and differential gear train.

As a power-transmitting means to be incorporated in the construction ofthe mechanical implementation of the power transmission apparatus of theinvention, there are various existing devices applicable. For example,in addition to the hydraulic power transmitting devices such as torqueconverter and fluid coupler already exemplified in the previousdescription paragraphs, other non-hydraulic devices can be incorporatedwith the epicyclic gear train to construct a mechanical implementationof the power transmission apparatus of the invention. Electromagneticpower-transmitting devices such as generator-motor set is among thosesuitable as it is also a power-transmitting system with a driving and adriven shaft.

FIG. 19 schematically illustrates a cross-sectional view of a mechanicalimplementation of the power transmission apparatus of the invention inwhich an induction machine is utilized as the power-transmitting device.In FIG. 19, a particular type of induction machine 210 is preferable.This induction machine 210 has a field element 211 constructed out of apermanent magnet system that can interact with a squirrel cage element212 similar in construction to those of a conventional induction motor.The permanent magnet system including at least a pair of permanentmagnets 216 can be arranged as either the frame or the rotor elementand, correspondingly, the squirrel cage element 212 can be either therotor or the frame element.

The induction machine 210 in the apparatus 200 of FIG. 19 is integratedwith the epicyclic gear train 220 in the manner described above to makeup a mechanical implementation of the power transmission apparatus ofthe invention. Specifically, the driving permanent magnet field element211 is connected to the ring gear 223 of the planetary gear train 220 bythe coupling framework 241, and the driven squirrel cage element 212 isconnected to the carrier gear 222 by the coupling shaft 242. Such apower transmission apparatus may be used as the transmission box ofsmall internal combustion engine-driven vehicles if adequate powerrating can be achieved utilizing permanent magnets with sufficientmagnetic flux intensity.

Other power-transmitting devices such as eddy-current coupler and othersbased on the principle of electromagnetism are also applicable. Allthese power-transmitting devices are considered to be similar both intheir general construction and functionality when they are incorporatedinto the power transmission apparatus of the invention as depicted inFIG. 11. They all possess a driving and a driven element forfacilitating the transmission of mechanical power.

The Electromagnetic Implementation of the Apparatus

As a generalized power transmission apparatus capable of delivering goodperformance at the low-speed end of the full output operating speedrange, there is an electromagnetic implementation of the invention alsofeasible in addition to the mechanical implementation described above.The generalized apparatus for power transmission of the inventionillustrated in FIG. 1, as described above, is capable of receiving anexternal power at its input end via input 131 and delivering power to anexternal load at its output end via output 132. An electromagneticimplementation of the power transmission apparatus of the invention isdefined to be one that incorporates an electromagneticpower-transmitting device and an electrical interaction redistributingmechanism implementing the interaction redistributionelectromagnetically. The electrical interaction redistributing mechanismcontrols the electric power supply to functioning elements of theelectromagnetic power-transmitting device for implementing theredistribution of electromagnetic power transmission interactionperformed. The two constituent parts are integrated togetherstructurally in a manner according to the invention to form an apparatusthat is operated as a power transmission system.

Though the power-transmitting device is limited to the electromagnetictype, the usefulness of this electromagnetic implementation of theapparatus of the invention is more versatile than the mechanicalimplementation described above. Due to the nature of the electromagneticpower-transmitting device incorporated, various electromagneticimplementations of the apparatus are capable of manipulating the powertransmission of either the mechanical-to-mechanical,electrical-to-mechanical, mechanical-to-electrical orelectrical-to-electrical mode. And, as mentioned above, theelectromagnetic implementation is also capable of manipulating the powertransmission in the reversed direction of power flow in many occasions,and thereby enabled to implement power regeneration.

In the electromagnetic implementation of the apparatus of the invention,the transmission of power, either electrical or mechanical, also relieson the electromagnetic interaction between the functioning elements ofthe electromagnetic power-transmitting device. Typical electromagneticpower-transmitting devices, generally known as electric machines orcouplers, have two interacting functioning elements usually arranged inthe form of a field frame and a rotor. In the electromagneticpower-transmitting device used to construct an electromagneticimplementation of the apparatus, the redistribution of theelectromagnetic interaction between the two elements of the device ontothe output of the apparatus is achieved by allowing both of the elementsto have their respective established magnetic field rotatable withrespect to the elements themselves. This relative rotation results in adifference between the angular speeds of the physical bodies of the twoelements that permits the two magnetic fields of the two electromagneticelements to be aligned for interaction while allowing the output of theapparatus to operate at its output angular speed. The extent of theangular speed of the relative rotation is adjustable and iscorrespondent to the angular speed of the output of the powertransmission apparatus. The capability of this adjustable relativerotation is provided by the interaction redistributing mechanism for theapparatus to be described in the following paragraphs. The other elementof the power-transmitting device is simply excited to establish its ownmagnetic field so as to interact with that established by the one thatis commutated.

The electromagnetic interaction redistributing mechanism for theelectromagnetic implementation of the power transmission apparatus ofthe invention is a rotary commutator. The rotary commutator is used toprovide electrical excitation to the windings of one of the interactingelements, the commutated element, of the electromagneticpower-transmitting device. The provision of electrical excitation to thecommutated element is in a switched manner in order to effect theredistribution of the electromagnetic interaction. The commutatedelement, with its magnetic field established by the excitationcontrolled by the rotary commutator, is thus capable of interacting withthe magnetic field of the other of the two elements, the not-commutatedelement which is also properly excited, in order to effect the powertransmission in the electromagnetic power-transmitting device.

The distinguished and essential characteristics of the electromagneticimplementation of the power transmission apparatus of the invention isthat the rotary commutator responsible for exciting the windings of thecommutated elements of the power-transmitting device is rotary as theapparatus operates. Excitation of the windings in the commutated elementas switched by the rotary commutator sets up an imaginary commutationorientation vector indicative of the angular position of the magneticfield produced by the commutated electromagnetic element. Thisorientation vector is rotary as the apparatus operates to transmit powersince the entire commutator system is itself rotary.

Note that when a DC excitation is supplied via the rotary commutator tothe commutated element, the established magnetic field does appear to berotary with respect to the physical body of the commutated element asthe entire rotary commutator rotates when the apparatus operates.However, when an AC excitation is used, the magnetic field establishedby the commutated element is itself rotary with respect to the imaginarycommutation orientation vector, namely with respect to the rotarycommutator. The rotational angular speed of the magnetic field is thusthe additive result of the rotation of the commutator and the frequencyof the AC excitation. As mentioned, DC current is, in fact, a specialcase of the AC current that is alternating with zero frequency.

In terms of the basic components used, two types, namely mechanical andpower electronic type, of rotary commutators are feasible forincorporation into the electromagnetic implementation of the powertransmission apparatus of the invention. In a mechanical rotarycommutator, one or more pairs of electrically conductive brushes arecarried by a brush cage, and the entire commutator may rotate as thebrush cage rotates when the apparatus operates. The rotation of therotary commutator effects the switching of the excitation power into thecommutated element of the electromagnetic power-transmitting device usedto construct the apparatus of the invention. In a power electronicsrotary commutator, a number of semiconductor power electronics switchesare controlled in a scheme so as to effect the switching of theexcitation power into the commutated interaction element of theelectromagnetic power-transmitting device. The electronic commutation issubstantially effected in the same manner as that by the mechanical typerotary commutator. In effect, the power electronics type of rotarycommutator implements the same switching pattern for the windings of thecommutated electromagnetic element as that achieved by its mechanicalcounterpart.

FIG. 20 illustrates the equivalent angular speed/gear ratio diagram forthe elements of the power-transmitting device and the interactionredistributing mechanism of an electromagnetic implementation of thepower transmission apparatus of the invention. The axis of abscissaerepresents the effective output-to-input gearing ratio of the apparatus,while the axis of ordinates represents the normalized angular speed ofthe functioning elements of the power-transmitting device and the rotarycommutator. Similar as in the discussion for the mechanicalimplementation, the input power is assumed to be driving the input ofthe electromagnetic implementation of the apparatus at a fixed angularspeed, along the input speed line 101 at the unity normalized angularspeed. The output of the apparatus may move along the output speed line102, representing that the apparatus is driving its load at differentgear ratios. Again, there are occasions when the gear ratio goes beyondunity as the output outruns the input, or become negative as the outputgoes in the reverse direction with respect to that of the input.

Since the electromagnetic implementation of the power transmissionapparatus of the invention may be involved in the transmission of bothmechanical and electrical power, therefore the unit of frequency, Hz, isused for measurement on the y-axis before normalization. This unit canbe conveniently converted into the rotational speed of the rotary shaftsuch as revolution-per-minute (RPM) when mechanical power in relation tothe rotation of the physical bodies. On the other hand, Hz itself is thestandard unit for representing one important characteristics of an ACelectrical power.

FIG. 21 illustrates a generalized electromagnetic implementation of thepower transmission apparatus of the invention as depicted in FIG. 1. Theapparatus 300 comprises an electromagnetic power-transmitting means 310and a rotary commutator 320, which is utilized as the electromagneticinteraction redistributing means. The electromagnetic power-transmittingmeans 310 is comprised of two electromagnetic interaction elements. Oneof the two elements, element 312 is the driving element that operates ata driving angular speed and transmits the power to the other, element311, which is the driven element that operates at a driven angularspeed, so as to implement the interaction of electromagnetic powertransmission between the two, under conditioning schemes controlled bythe rotary commutator 320. Note that the perspective diagram of FIG. 21shows that the driven element 311 identified by phantom lines isenclosed inside the driving element 312.

The power transmitted inside the electromagnetic power-transmittingmeans 310 is received from an external power source 381 via an input331_(M) or 331_(E) of the apparatus. The electromagneticpower-transmitting means 310 is integrated with the electromagneticinteraction redistributing means 320 to make up the electromagneticpower transmission apparatus. The power received by the electromagneticpower-transmitting means 310 from the external power source 381 isredistributed by the electromagnetic interaction redistributing means320 onto an output 332_(M) or 332_(E) of the apparatus and delivered toan external load 382.

The electromagnetic interaction redistributing means 320 is a rotarycommutator for magnetizing one of the two electromagnetic elements, 311,which is the commutated element. The rotary commutator 320 is integratedwith the two electromagnetic elements 311 and 312 of the electromagneticpower-transmitting means 310, in which the rotary commutator 320operates at a commutation angular speed to magnetize the commutatedelectromagnetic element 311 and establishes a first rotating magneticfield rotating at an angular speed that is synchronous with the angularspeed of a second rotating magnetic field established by theelectromagnetic element 312 not being commutated. The power-transmittingelectromagnetic interaction of the power-transmitting means 310operating at the synchronized angular speed of the two rotating magneticfields is redistributed onto the output 332_(M) or 332_(E) by the rotarycommutator 320, and the output delivers the power from theelectromagnetic power-transmitting means 310 to the external load 382 atan output angular speed.

Note, in FIG. 21, that two inputs 331_(M) and 331_(E) and two outputs332_(M) and 332_(E) are shown to be present for the apparatus at theinput and output ends respectively. This is to schematically accommodateto the fact that both the input and the output of the power transmissionapparatus of the invention is capable of handling either mechanical orelectrical power. In case mechanical power is received or delivered bythe apparatus, corresponding input or output rotary shaft is used. Incase electrical power is received or delivered, corresponding input oroutput electrical lead is used. In some embodiments of the apparatus ofthe invention capable of performing multiple modes of powertransmission, both the rotary shaft and the electrical lead for eitherinput or output may be used.

In the electromagnetic implementation of FIG. 21, the first, 311, of thetwo electromagnetic elements of the power-transmitting device 310 thatis commutated by the rotary commutator 320 is amagnetization-redistributing electromagnetic winding assembly, and thesecond element 312 without commutation is an electromagnetic assemblymade up of windings. As will be explained in the following paragraphswith reference to the corresponding drawings, the commutated windingassembly of the first electromagnetic element 311 may assume one of twopossible constructions, and the electromagnetic assembly for the secondelement 312 may take the form of one of three possible constructions.Various combinations of these two electromagnetic elements, whenintegrated with the electromagnetic interaction redistributing mechanismand properly excited in accordance with control schemes of theinvention, may be utilized in each of the four possible powertransmission modes involving both the mechanical and electrical power.

The magnetization-redistributing electromagnetic winding assembly forthe first electromagnetic element 311 may be a DC armature similar instructure to the DC-excited armature of a conventional DC machine if DCexcitation is intended. Or, the element 311 may also be amultiple-commutation AC armature that can be excited via more than onepair of commutator brushes or the power electronics equivalent of therotary commutator if poly-phase AC power is used for its excitation. Ineither case, this winding assembly can be excited by the rotarycommutator 320 for establishing the first rotating magnetic field.

The electromagnetic assembly used as the second electromagnetic element312 may be an electromagnet winding assembly energized by a DC power andfunctions as an electromagnet. It can also be a poly-phase windingexcited by a poly-phase AC power. Or, it may simply be a permanentmagnet assembly made up of one or more properly magnetized magnets thatcreates a magnetic field.

FIGS. 22-27 respectively illustrate the embodiments of theelectromagnetic implementation of the power transmission apparatus ofthe invention based on the electromagnetic power-transmitting deviceemploying the three types of electromagnetic assembly and two types ofmagnetization-redistributing winding assembly described above. Each ofthe basic structural configuration of the power transmission apparatusof FIGS. 22-27 may be suitable for use in all or some of the four modesof power transmission involving both mechanical and electrical power. Insubstantial application situations, some of the embodiments may be morepreferable than the others.

Note that the presence of both the mechanical rotary shaft and theelectrical leads at both the input and output ends of the apparatus maynot be necessary for some of the four modes of power transmission.Though in some transmission modes the electrical leads may be requiredto provide excitation power to the specific winding assembly of theelectromagnetic element in order to effect either the input or theoutput of the mechanical power, they are, however, not considered to bethe major power input or output. These excitation power normally consumeonly a small percentage of the total electrical power input to thesystem and are categorized as auxiliary power consumption inevitable forthe implementation of an ideal machine as a real apparatus. Similarly,in some transmission modes the rotary shaft may be shown present in thedrawing in which the apparatus inputs or outputs electrical power. Inany case, although not discussed in detail, and as is appreciable forthose skilled in the art, it is still possible that the electromagneticimplementation of the power transmission apparatus of the invention beoperated to handle both the mechanical and electrical power input and/oroutput simultaneously if any such requirement exists.

FIG. 22 illustrates an embodiment of the generalized electromagneticimplementation of the power transmission apparatus of the invention asdepicted in FIG. 21. The basic structural configuration of the powertransmission apparatus of FIG. 22 is suitable for use in all four modesof power transmission, which involves both mechanical and electricalpower. In this embodiment, the magnetization-redistributingelectromagnetic winding assembly 311 used as the commutated firstelectromagnetic element of the electromagnetic power-transmitting deviceis an AC armature. This AC armature 311 is comprised of a number ofelectrically-switchable AC windings 318. Each of the AC windings 318 canbe excited by a poly-phase AC current switchingly supplied by the rotarycommutator 320 in an orderly manner so as to establish the firstrotating magnetic field. In order to switch the poly-phase AC power intothe winding assembly 311, there are more than one pair of conductivebrushes 321 or their power electronics equivalent in the rotarycommutator 320.

The electromagnetic assembly 312 used as the second and non-commutatedelectromagnetic element is a poly-phase winding having a winding 317that can be excited by a poly-phase AC current in order to establish thesecond rotating magnetic field. An angular speed of the imaginarycommutation orientation vector of the rotary commutator 320 not shown inthe drawing may be asynchronous with the angular speed of the secondrotating magnetic field established by the electromagnetic assembly 312of the second electromagnetic element. Specifically, the orientationvector angular speed is equal to the difference of the angular speed ofthe second rotating magnetic field and the angular speed of thepoly-phase AC current supplied by the rotary commutator 320 to the firstelectromagnetic element 311.

When the electromagnetic implementation of the apparatus as depicted inFIG. 22 is used to implement mechanical-to-mechanical powertransmission, the physical body of the electromagnetic assembly 312 canbe driven by an external mechanical power source via its rotary shaft331_(M) In this case, the electrical lead 331_(E) is used to supply theexcitation power for the electromagnetic assembly 312 to establish itsmagnetic field. As the physical body of this second electromagneticelement 312 is driven rotating, its excitation can be provided by eitherAC or DC electrical power. This excitation is supplied from the externalexcitation power source utilizing the carbon brush-slip ring arrangementof the non-commutated element excitation means generally identified by350. Each of the fixed carbon brushes 351 contacts its correspondingslip ring 352 that rotates together with the physical body of theelectromagnetic assembly 312. An electric power supply network 353 fixedto or embedded in the physical body of the element 312 distributes theexcitation power to the windings 317 of the non-commutated element 312.

In case DC excitation is adopted for the second electromagnetic element312, the angular speed of the magnetic field established by this secondelement is simply the input rotational speed of the external powersource as supplied by the external mechanical power source via the inputrotary shaft 331_(M). In case of AC excitation, the angular speed ofthis magnetic field is the additive result of the angular speed of theexternal mechanical power source and that of the AC excitation.

On the other hand, the physical body of the commutated element 311 canbe connected to the output shaft 332_(M) of the apparatus and used todrive an external mechanical load. The commutated element 311 receivesits excitation via the electrical lead 332_(E) connected through therotary commutator 320. This excitation is supplied from the externalexcitation power source utilizing another carbon-slip ring mechanism360. Similar to 350, the carbon brush-slip ring excitation mechanism 360employs fixed carbon brushes 361 and slip rings 362 to facilitateexcitation power supply to the commutated element 311. Since theimaginary commutation orientation vector is rotary, the slip rings 362of the excitation mechanism 360 are fixed to the brush cage 322 of therotary commutator 320. This arrangement allows the brushes 321 of therotary commutator 320 which are attached to the brush cage 322 forrotation in the controlled schemes to receive the excitation electricalpower from external, although its detailed mechanism is not shown in thedrawing. An electrical power supply network 363 fixed to or embedded inthe physical body of the element 311 distributes the excitation power tothe windings 318 of the commutated element 311.

Since the physical body of the commutated element 311 is also rotatingas the apparatus operates to transmit mechanical power, the angularspeed of the imaginary commutation orientation vector required foroperating the apparatus can be determined from the angular speed of theoutput shaft 332_(M) and that of its excitation. In case that DCexcitation is supplied to the commutated element 311, the requiredangular speed of the commutation orientation vector becomes equal tothat of the magnetic field established by the second electromagneticelement 312.

Note in the drawing of FIG. 22 that suitable bearings means 333 areprovided at the necessary locations within the apparatus. This permitssmooth lubricated relative rotational motions between the variouselements of the power-transmitting means 310 and the interactionredistributing means 320.

The power transmission apparatus of FIG. 22 is also suitable for use inelectrical-to-mechanical power transmission. In this case, the physicalbody of the electromagnetic assembly 312 is fixed stationary, and itselectrical lead 331_(E) is electrically coupled to the externalelectrical power source for supplying the primary electrical power tothe electromagnetic assembly 312 itself in order to establish itsdriving magnetic field. Excitation power is supplied utilizing theslip-ring mechanism 350, or a simplified electrical distribution systemas the physical body of the electromagnetic assembly 312 is fixedstationary. Since the physical body of this second electromagneticelement 312 is held stationary, the angular speed of the magnetic fieldgenerated in itself by the power excitation is determined directly bythe frequency of the electrical power excitation.

Meanwhile, the physical body of the commutated element 311 can beconnected to the output shaft 332_(M) of the apparatus and used to drivethe external mechanical load. The commutated element 311 receives itsexcitation via the electrical lead 332_(E) connected through the rotarycommutator 320. Excitation power is supplied utilizing the slip-ringmechanism 360. As is in the case of mechanical-to-mechanicaltransmission, since the physical body of the commutated element 311 isrotating as the apparatus operates to transmit power, the angular speedof the imaginary commutation orientation vector can be determined fromthe angular speed of the output shaft 332_(M) and that of itsexcitation. In case that DC excitation is supplied to the commutatedelement 311, the angular speed of the commutation orientation vectorbecomes equal to that of the magnetic field established by the secondelectromagnetic element 312.

The power transmission apparatus of FIG. 22 is further suitable for usein mechanical-to-electrical power transmission. In this case, thephysical body of the electromagnetic assembly 312 can be driven by theexternal mechanical power source via its rotary shaft 331_(M) Theelectrical lead 331_(E) is used to supply the excitation power for theelectromagnetic assembly 312 in order to establish its magnetic field.As the physical body of this second electromagnetic element 312 isdriven rotating, its excitation can be provided by either AC or DCelectrical power. Slip-ring mechanism 350 supplies excitation power tothe windings 317 of the assembly 312. In case of DC excitation, theangular speed of the magnetic field established by this second elementis simply the input rotational speed of the external power source. Incase of AC excitation, the angular speed of the magnetic field is theadditive result of the angular speed of the external mechanical powersource and that of the AC excitation.

Meanwhile, the physical body of the commutated element 311 is fixedstationary, and the electrical lead 332_(E) connected through the rotarycommutator 320 becomes the output of the power transmission apparatusthat can drive an external electrical load. Electrical power collectingmeans simpler in construction than the slip-ring mechanism 360 can beused to collect the generated electrical power. Current flowing in thewindings 318 of the first element 311 as switched by the rotarycommutator 320 establishes a magnetic field that interacts with the onegenerated by the second element 312 to effect themechanical-to-electrical mode of power transmission.

The power transmission apparatus of FIG. 22 may also be used forelectrical-to-electrical power transmission. In this case, the physicalbody of the electromagnetic assembly 312 is fixed stationary, and itselectrical lead 331_(E) is electrically coupled to the externalelectrical power source for supplying the primary electrical power tothe electromagnetic assembly 312 in order to establish its drivingmagnetic field. As physical body of this second electromagnetic elementis held stationary, the angular speed of the magnetic field generated inthe electromagnetic assembly 312 by the power excitation is determineddirectly by the frequency of the electrical power.

On the other hand, the physical body of the commutated element 311 isalso fixed stationary, and the electrical lead 332_(E) connected via therotary commutator 320 becomes the output of the apparatus that can drivean external electrical load. Current flowing in the windings of thefirst element 311 as switched by the rotary commutator 320 establishes amagnetic field that interacts with the one generated by the secondelement 312 to effect the electrical-to-electrical mode of powertransmission. The slip-ring mechanisms 350 and 360 in this electricalpower transmission can be simplified, since the physical bodies of boththe electromagnetic assembly 312 and the commutated element 311 arefixed stationary.

FIG. 23 illustrate another embodiment of the electromagneticimplementation of the power transmission apparatus of the invention ofFIG. 21. This is an apparatus only slightly different from that of FIG.22. Specifically, instead of the AC armature, themagnetization-redistributing electromagnetic winding assembly 311 usedas the commutated first electromagnetic element of the electromagneticpower-transmitting device is a DC armature, which is comprised of anumber of electrically-switchable DC windings 319. The electromagneticassembly 312 used as the second electromagnetic element is a poly-phasewinding similar to that of FIG. 22. Since, as mentioned above, DC isconsidered to be a special case of AC, it can be expected that thisembodiment is a special case, and in effect a simplified version, of theapparatus of FIG. 22.

In order to switch the DC power into the winding assembly 311, only onepair of conductive brushes 321 or their power electronic equivalent arerequired in the rotary commutator 320. To operate this apparatus, theangular speed of the imaginary commutation orientation vector of therotary commutator 320 needs to be synchronous to the angular speed ofthe second rotating magnetic field established by the electromagneticassembly 312 of the electromagnetic power-transmitting device 310.Specifically, the angular speed of the orientation vector is equal tothe angular speed of the second magnetic field. This can be achieved bycontrolling the angular speed of the brush cage 322 that holds anddrives the brushes 321 in the manipulated switching scheme.

Thus, when operated in either the mechanical-to-mechanical,electrical-to-mechanical or mechanical-to-electrical mode oftransmission, the excitation in the commutated element 311 can be simpleDC power, and the control of the imaginary commutation orientationvector is simply required to be synchronous to the rotation of themagnetic field established by the electromagnetic assembly 312.

When operated in the electrical-to-electrical mode of powertransmission, the output of the apparatus, electrical leads 332_(E)connected via the rotary commutator 320, produces only DC power if theimaginary commutation orientation vector of the rotary commutator 320 ismaintained synchronous to the rotation of the magnetic field produced bythe powering electromagnetic assembly 312. If, however, the orientationvector is controlled to be asynchronous to the powering magnetic field,the generated electrical power becomes an AC electrical power. Thefrequency of this AC power is determined by the subtractive result ofthe angular speeds of the input electrical power and that of theorientation vector.

FIG. 24 illustrates yet another embodiment of the electromagneticimplementation of the power transmission apparatus of the inventionfundamentally outlined in FIG. 21. This is an apparatus also slightlydifferent from that of FIG. 22. The difference being the replacement ofthe poly-phase winding for the electromagnetic assembly 312 by anelectromagnet winding assembly. Such an electromagnet winding assemblyis similar to the stator winding of a DC machine and, like anelectromagnet, produces a magnetic field non-rotatable with respect toits physical body when energized.

Such an apparatus is suitable for mechanical-to-mechanical andmechanical-to-electrical mode of power transmission. In these two modes,the apparatus behaves similar to that of FIG. 22 except that theexcitation to the electromagnetic assembly 312 is DC. This apparatus isnot preferred for operation in the electrical-to-mechanical mode oftransmission, assuming that the physical body of the electromagneticassembly 312 is fixed stationary. When thus operated, the apparatus ofFIG. 24 becomes substantially the same as a conventional DC motor. Ifboth physical bodies of the electromagnet winding assembly 312 and theAC armature 311 of this embodiment is fixed, theelectrical-to-electrical mode of transmission is not feasible sincethere is no transformer operation exists in the system. This is becausethat the magnetic field established by the electromagnet windingassembly 312 is not rotating with respect to the conductors of the ACarmature 311 at all.

FIG. 25 illustrates another embodiment of the electromagneticimplementation of the power transmission apparatus of the inventionoutlined in FIG. 21. This apparatus differs from the apparatus of FIG.24 only in that the magnetization-redistributing electromagnetic windingassembly 311 is a DC armature instead of AC. As such, thecharacteristics of this apparatus is basically the same as theembodiment of FIG. 24. Apparently, the excitation to the AC armature 311in the embodiment of FIG. 24 is preferably poly-phase AC electricalpower, while the DC armature 31 1 of this embodiment requires DCexcitation.

FIG. 26 illustrates still yet another embodiment of the electromagneticimplementation of the apparatus of the invention. This apparatus iseffectively the same as that of FIG. 24 except that a permanent magnetassembly including at least a pair of permanent magnets 316 for theelectromagnetic assembly of FIG. 21 replaces the electromagnet windingassembly of FIG. 24. Electrical excitation to the electromagneticassembly 312 is thus not required, and the system electricalconfiguration becomes simplified. However, the electromagnet windingassembly of the embodiment of FIG. 24 is capable of providing magneticfield with stronger field intensity than permanent magnets as itsexcitation power is increased proportionally. Thus, power rating of theapparatus of FIG. 26 is limited to a level the material technology ofpermanent magnet can provide.

The electromagnetic implementation of the power transmission apparatusof the invention as exemplified in FIG. 27 is a further-simplifiedversion of that of FIG. 26. A DC armature 311 for themagnetization-redistributing electromagnetic winding assembly of FIG. 21replaces the AC armature 311 of FIG. 26. Thus, the operatingcharacteristics of this embodiment of FIG.24 is substantially the sameas that of FIG. 27 except that DC excitation is used for the DC armature311.

Each of the embodiment as outlined in FIGS. 22-27, when operated in themechanical-to-mechanical mode of power transmission, can be utilized asa mechanical transmission device for converting an input mechanicalpower at one speed/torque combination into an output at another. This isin effect equivalent in function to that of the traditional mechanicalpower-transmitting devices such as hydraulic torque converters orgenerator-motor sets found application in automotive and diesel-electriclocomotives. However, low-speed performance of the apparatus of theinvention as exemplified in these embodiments may enjoy high efficiencysince the power-transmitting electromagnetic devices incorporated arerestricted by the rotary commutator to operate within their optimizedspeed range.

When operated in the electrical-to-mechanical mode of powertransmission, each of these embodiments are in effect a new version ofelectric motor operating under the principle of electromagnetism. Theseare thus electric machines directly applicable for electric tractiondrive applications without sophisticated power electronics such as PWM.However, each of these apparatus of the invention is capable ofdelivering good low-speed performance since the rotary commutator allowsthe incorporated electromagnetic power-transmitting device, effectivelya modified version of the conventional electric machine, to operate inthe optimized speed range of that of a conventional motor.

When operated in the mechanical-to-electrical mode of powertransmission, each of these embodiments is in effect a new version ofelectric generator operating under the principle of electromagnetism.Each of these apparatus of the invention is capable of delivering goodlow-speed electric generation performance since the rotary commutatorallows the electromagnetic power-transmitting device, effectively amodified version of the traditional electric machine, to operate in theoptimized speed range of that of a conventional generator.

In the mechanical-to-electrical and electrical-to-mechanical modes ofpower transmission performed by the embodiments of FIGS. 22-27, thephase angle between the two magnetic fields established by the twointeracting elements of the electromagnetic power-transmitting devicecan be utilized as a parameter for controlling the rate of powertransmission as performed by the apparatus. In general, the drivingmagnetic field of the electromagnetic assembly 312 leads the driven ofthe commutated element 311 for an angle that is proportional to thepower transmitted. In other words, the larger the leading phase angle,the larger the power transmitted. If the one electromagnetic elementthat was originally leading becomes lagging, then the direction of powertransmission is reversed, and the apparatus operates to regenerate.

In the mechanical-to-mechanical mode of transmission of the embodiments,the phase angle between the magnetic fields is settled to an angledetermined by the input and load conditions. In theelectrical-to-electrical mode of transmission in which the commutatedelement is a DC armature, the phase angle can be used to control theoutput voltage of the generated DC power if the imaginary commutationorientation vector is controlled to rotate synchronous to the powermagnetic field of the electromagnetic assembly. On the other hand, ifthe orientation vector is operated asynchronous to the power magneticfield, then the apparatus simply produces a single-phase AC electricalpower. This assumes that DC armature has only one pair of commutatorbrushes or their power electronic equivalent for picking up thegenerated electrical power. To facilitate such phase angle control,suitable control mechanism can be provided and integrated into therotary commutator system.

When operated in the electrical-to-electrical mode of powertransmission, each of the applicable embodiments of FIGS. 22-27 is ineffect a frequency converter that operates substantially as atransformer. The angular speed of the imaginary commutation orientationvector of the rotary commutator 320 can be utilized as a controllingparameter to determine the frequency of the output AC power. If theorientation vector is controlled to be synchronous with the rotation ofthe driving magnetic field of the second electromagnetic element 312,then the output electrical power delivered by the electrical lead332_(E) connected through the rotary commutator 320 is an AC power ofzero alternating frequency. Specifically, this is DC electrical power.

When, however, the imaginary commutation orientation vector iscontrolled to be rotating at an angular speed that is either faster orslower than the rotating magnetic field of the electromagnetic assembly312, then the frequency of the AC power as picked up by the rotarycommutator 320 from the commutated element 311 is the difference betweenthe two. In this case, the apparatus becomes a poly-phase frequencyconverter capable of converting a poly-phase AC electric power of aninput frequency into another with an output frequency different from theinput.

When the apparatus exemplified in FIG. 21 or, in other words, each ofthe specific embodiments of FIGS. 22-27 is operated in themechanical-to-mechanical and electrical-to-mechanical modes of powertransmission, the apparatus exhibits a natural tendency of automaticacceleration as the input mechanical or electrical power is received bythe apparatus. The power received by the apparatus is transmitted anddelivered to the external mechanical load, which accelerates along thegear ratio diagram of FIG. 20, assuming the external power source isdriving the apparatus at a constant angular speed. In the case of theelectrical-tom-mechanical power transmission, this is an advantageouscharacteristics suitable for vehicular and industrial electric tractiondrive applications. In the case of mechanical-to-mechanical powertransmission, this tendency is an advantage similar as was in the caseof the mechanical implementation of the power transmission apparatus ofthe invention described above.

In the embodiments outlined in FIGS. 22-27 and described above, therotary commutator integrated with the electromagnetic power-transmittingdevice can be either a mechanical or a power electronics rotarycommutator. Mechanical rotary commutator is relatively simple inconstruction that can be integrated with the power-transmitting deviceand is also easy to operate. However, mechanical rotary commutatorsoperating via frictional contact between the carbon brushes and thecommutator ring require regular maintenance in order to prevent andreduce problems caused by short-circuiting. On the other hand, a powerelectronics rotary commutator based on semiconductor power electronicswitching circuitry is relatively more sophisticated both to constructand integrate into the system. However, a power electronics rotarycommutator can more readily be incorporated into a digital controlsystem so that the power transmission apparatus can be operateddigitally. In addition, there is no carbon brush wear problem associatedwith power electronics rotary commutators. FIGS. 28 and 29 respectivelyexemplify a mechanical and a power electronics rotary commutator for theelectromagnetic implementation of the power transmission apparatus ofthe invention.

FIG. 28 illustrates a mechanical type of rotary commutator that can beintegrated with the electromagnetic power-transmitting devices such asthose exemplified in the apparatus embodiments of FIGS. 22-27. Theperspective view of FIG. 28 only shows the major components of themechanical rotary commutator. The mechanical rotary commutator 320_(M)is comprised of a number of, for example, three pairs of carbon brushesand a brush cage. In the drawing, only one pair of brushes 321 is shownfixed to the inner circumferential surface of the brush cage 322. Thenumber of pairs of carbon brushes is dependent on the configuration ofthe armature utilized as the magnetization-redistributingelectromagnetic winding assembly 311 of the embodiments of FIGS. 22-27.If the commutated armature 311 is DC-excited, a single pair of carbonbrushes is sufficient. If the commutated armature 311 requirespoly-phase AC excitation, more than one pair of brushes are necessary.

The brush cage 322 is a framework used as the carrier for the carbonbrushes. The brush cage 322 has, for example, a substantially hollowcylindrical configuration, and each of the carbon brushes 321 isinstalled on the inner circumferential surface of the cage at therespective designated location. Each of the carbon brushes 321 isinstalled to the cage 322 by, for example, insertion into a containerhousing 323. Each of these housings 323 provides a holding means for itscorresponding carbon brush 321 on the inner surface of the cage 322, andpressure means such a spring installed between the carbon brush 321 andthe bottom of the housing 323 presses the contacting surface of thecarbon brush 321 against the commutator ring 315 of the armature 311 asthe cage 322 is assembled in its proper position in the system. Thepressure means also permits a carbon brush 321 to move inwards along theradial axis of the cage 322 as it is worn out due to prolongedfrictional operation.

The central hollow space inside the brush cage 322 of the rotarycommutator 320_(M) allows for the insertion of the shaft 332_(M) and thecommutator ring 315 of the armature 311. When properly assembled, eachof the brushes 321 carried by the cage 322 can be aligned with thecommutating surface of the commutator ring 315 and allowing pressurizedcontact of the brushes 321 against the commutator ring 315 on theirrespectively designated and angularly spaced locations.

When external electrical power source is required to excite the armature311 of the apparatus, each of the carbon brush container housing 323 canbe electrically connected to a corresponding slip rings 362 fixed to theouter circumferential surface of the brush cage 322, as is schematicallyshown by the electrical connection 364 penetrating through the wall ofthe cylindrical body of the cage 322. The reason to use slip rings 362is based on the fact that the rotary commutator 320_(M) for theapparatus of the invention is rotary itself. In other words, the rotarycommutator 320_(M) has its brush cage 322 rotates with respect to thechassis of the apparatus as the apparatus operates. Electricallyconductive paths established by the corresponding groups of carbon brush321, the brush container housing 323 and the slip ring 362 may be usedto provide the excitation power from the external excitation powersource to the windings 318 of the armature 311 via the commutator ring315.

Rotational speed of the brush cage 322 of the rotary commutator 320_(M)is controlled under schemes depending on the structural configuration ofthe apparatus of the invention. The speed is also dependent on the modeof power transmission and the nature of the power involved such asfrequency of AC power. When the rotary commutator 320_(M) is required torotate so that its imaginary commutation orientation vector determinedby one of the brush pairs rotates asynchronous to that of the magneticfield produced by the electromagnetic assembly not shown in FIG. 28, ingeneral, a controlled rotary drive is needed to drive the brush cage 322for rotation according to the speed control scheme.

In a special case that the rotary commutator 320_(M) is required torotate synchronous to the physical body of the electromagnetic assembly312 of the non-commutated element, the brush cage 322 can simply befixed to the physical body of the assembly 312 so that both rotatetogether synchronously. For example, in the embodiment of FIG. 27 inwhich permanent magnets 316 of the non-commutated element 312 is used togenerate the first magnetic field, its brush cage 322 can be fixeddirectly to the frame of the element 312.

FIG. 29 illustrates the schematic diagram of a power electronic type ofrotary commutator that can be integrated into the electromagneticimplementations of the apparatus such as those exemplified in theembodiments of FIGS. 22-27. The power electronics rotary commutator320_(E) is comprised of a semiconductor switch array 325 and a controllogic 328. This semiconductor commutator 320_(E) may be carried onboardthe physical body of the commutated element, 311 of FIGS. 22-27, so thatits semiconductor switches 325_(1A) -325_(1D), 325_(2A) -325_(2D), . . .and 325_(NA) -325_(ND) can be connected to the windings 319₁, 319₂, . .. and 319_(N) of element 311 shown organized in the schematic diagram asthe winding array 319 for implementing the necessary excitationswitching scheme. This assumes a total of N windings are wound in thecommutated element 311. The switch array 325 is responsible forsupplying excitation electrical power to the windings 319₁, 319₂, . . .and 319_(N) of the commutated element 311. In case the excitation powersource is provided external to the apparatus, a pair of slip rings 362can be used to receive excitation from the external power source 381 viatheir corresponding carbon brushes 361.

The switching scheme implemented by the switch array 325 is undercontrol of the control logic 328. The control logic 328 implements itscontrol scheme based on the angular speed and position of the magneticfield generated by the non-commutated electromagnetic assembly 312.Angular position and speed of the magnetic field established by theassembly 312 may be detected utilizing a sensor arrangement 327, whichmay be coupled to the control logic 328 via, for example, photoelectriccoupling, for relaying its detected signals.

In the depicted circuitry example of FIG. 29, the power electronicsrotary commutator 320_(E) is equivalent in function to a mechanicalcounterpart having a single pair of brushes and receiving DC excitation,such as the one of FIG. 28. An external DC power source 381 provides theexcitation electrical power via the rotary frictional contact of theslip rings 362 and their corresponding carbon brushes 361. Thesemiconductor switches in the switch array 325 are organized into twogroups, i.e. the positive 325_(P) and the negative group 325_(N), witheach group including half the total number of switches. Each of thewindings 319₁, 319₂, . . . and 319_(N) of the commutated element 311 hastwo terminals that require switched connection to the excitation powersource 381. Each of its two terminals needs to be switched onto both thepositive and negative terminals of the excitation power source 381 inthe scheme governed by the control logic 328. Assuming the use of SCR(silicon-controlled rectifier) as the semiconductor switching element,each terminal of a winding of the commutated element 311 thus requirestwo SCR's to be connected to the positive and negative terminals of thepower source 381 in order to form a complete circuit loop so thatexcitation may take place. Thus, for a total of N windings in the array319, a total of 4N SCR switches are required in the switch array 325 inthis described example.

For example, consider the winding 319₁ in winding array 319. One of itstwo terminals 319_(1A) is allowed to be connected to both the positiveand negative terminals of the excitation power source 381 via the SCR325_(1A) and 325_(1C) respectively. The other terminal 319_(1B) is alsoallowed to be connected to the positive and negative terminals via SCR325_(1B) and 325_(1D) respectively. When the excitation requirement isfor the terminal 319_(1A) of winding 319₁ to be connected to thepositive terminal and the terminal 319_(1B) to the negative, the controllogic 328 turns on SCR 325_(1A) and 325_(1D) simultaneously by sendingthe corresponding gate signals to these two SCR's via the trigger signalbus 326. When it is required that the terminal 319_(1A) be connected tothe negative terminal and the terminal 319_(1B) to positive, SCR325_(C1) and 325_(1B) are turned on simultaneously. All other windings319₂ -319_(N) in the array 319 are connected to their respective SCR'sand controlled under similar schemes. Depending on the design, there canbe more than one windings in the array 319 excited simultaneously.Whatever the required switching pattern and its correspondingcontrolling scheme, the control logic 328 can be adequately programmedto govern the adequate turned-on and -off status of all the SCR's in theswitch array 325.

Similar as in the case of the mechanical implementation of the apparatusof the invention, there are occasion in which the driving and drivenroles of the two electromagnetic elements of the electromagneticpower-transmitting device are reversed within the same configurationalarrangement for a particular apparatus of the invention. This permitsthe reversed direction of power flow as compared to that when theapparatus is operating in the normal direction of input-output powerflow. This is possible based on the same principle as that of theconventional electric machines for which a motor is easily turned into agenerator when the load becomes driving the rotor shaft that wasoriginally delivering mechanical power.

For example, consider the situation in which the electromagneticimplementation of the apparatus of the invention depicted in FIG. 23 isoperated in the electrical-to-mechanical mode of power transmission. Inthe apparatus of FIG. 23, the electromagnetic assembly 312 is apoly-phase winding wound on its physical body that is fixed stationary.The magnetization-redistributing electromagnetic winding assembly 311 isa DC armature, which receives its excitation via the rotary commutator320. Assuming that the rotary commutator 320 is a mechanical rotarycommutator having one single pair of carbon brushes.

When power excitation is fed to the poly-phase winding of the assembly312 by the external electrical power source, it establishes a magneticfield with an angular speed determined by the frequency of the externalelectrical power source. This magnetic field drives the commutatedelement 311 via interaction with the other magnetic field established bythe element 311 feeding its excitation by the rotary commutator 320. Theimaginary commutation orientation vector of the rotary commutator 320,in this case the diametric axis of the pair of brushes, rotatessynchronous to the magnetic field of the electromagnetic assembly or, inother words, rotates at the angular speed converted from the frequencyof the external electrical power source. As described above, this allowsthe output shaft 332_(M) of the apparatus, the shaft of the commutatedelement 311, to drive the external mechanical load at any speed on thegear ratio axis of FIG. 20.

When the mechanical load becomes a mechanical power source and drivesthe rotary shaft 332_(M) of the commutated element 311, the poly-phasewinding of the electromagnetic assembly 312 may now generate apoly-phase AC power to drive an electrical load coupled thereto. Theregenerated AC electrical power can be controlled at the same frequencyas that of the original electrical power source regardless of theangular speed of the mechanical power source now present at the rotaryshaft of the commutated element 311. This can be achieved simply bycontrolling the angular speed of the imaginary commutation orientationvector at that particular angular speed of the original electrical powersource. The regenerated AC power can even be controlled to be in-phasewith the original external electrical power source simply by controllingthe commutation orientation vector to be at the required phase anglewith respect to the rotating magnetic field of the original powersource.

This ability to regenerate an AC electrical power is useful in manyindustrial and transportation applications. For example, consider thesituation in which the above-described electromagnetic implementation ofFIG. 23 is used as the traction motor of a railway locomotive when itoperates in the normal mode of electrical-to-mechanical powertransmission. Electrical system of such a regenerative traction drive isillustrated in FIG. 30.

Assuming that the poly-phase winding for the electromagnetic assembly312 is a two-phase system wound on the stationary stator frame of theapparatus, and a DC armature 311 for the magnetization-redistributingelectromagnetic winding assembly is constructed on the rotor. Thedrawing schematically shows that the rotor of the DC armature 311 iscoupled via a gearing system to the traction wheels of the railwayvehicle which represents the mechanical load 382 of the system. Althoughthe electrical power source 381 for electrified railway, as fed from theoverhead power line 385 using a pantograph 386, is single-phase AC, thesecond phase with a 90-degree phase lag may be conveniently available.This second power phase can be obtained utilizing a unity transformer387 feeding on the single-phase AC power source 381. This railwaytraction drive system operates in the electrical-to-mechanical mode ofpower transmission in the manner described in the previous paragraphs,extracting the single-phase AC line power from the utility company fordriving the train to accelerate or ascend grades.

Consider the situation in which the train decelerates or descendsgrades. The commutated rotor 311 now becomes driven by the kinetic orpotential energy of the train. By implementation of the controlprinciple described above under control of the system control logic 380,the system of FIG. 30 which is based on the electromagneticimplementation of the apparatus of the invention may now be operated inthe reversed direction of power flow. Mechanical power is now harnessedand may be directly fed back into the utility network distribution line385 through the overhead pantograph 386 of the train. This regenerativebraking is possible since all parameters of the regenerated AC power,including the frequency, the phase and the voltage can be controlled tobe compatible to that generated by the utility company which is presentin the distribution network.

In addition to the regenerative traction drive for electrified railway,electromagnetic implementation of the apparatus of the invention similarto that of FIG. 30 can be equally suitable for applications such ascogeneration and wind turbine power generation. Both the mechanicalpower produced by the steam turbine in the cogeneration facility and bythe wind turbines of the wind mill typically have the same nature ofchanging characteristics as that produced by the railway trains duringdeceleration and grade descent. One common requirement for theseapplications is that the generated AC electrical power must becompatible to that in the utility network. Failure to achieve this wouldintroduce high-frequency harmonics into the utility network that maydamage equipments and appliances connected nearby.

Though, electromagnetic implementations of the apparatus of theinvention for cogeneration and wind power generation typically operatein one direction of power flow only, i.e., in themechanical-to-electrical mode of transmission. Electrical system of anelectromagnetic implementation of the power transmission apparatus ofthe invention suitable for use as the electric generator for acogeneration facility or a wind turbine generator system would be verysimilar to that exemplified in FIG. 30. Though not described herein,there are many other applications that may take advantage of the natureof simple regeneration control of the electromagnetic implementation ofthe power transmission apparatus of the invention.

For practical considerations, the excitation power source required foreither or both of the electromagnetic interaction elements of theelectromagnetic power-transmitting device in various embodiments of theinvention may be incorporated directly into the apparatus itself. Forexample, the DC excitation power source, with its power ratingrelatively much smaller than the main power source, may be generated bya DC generator directly integrated in the apparatus itself.

Similar as is in the case of conventional electric machines, theelectromagnetic implementation of the power transmission apparatus ofthe invention is preferably constructed into a device with a cylindricalhollow frame element and a cylindrical rotor element. When assembled,the cylindrical rotor element can be inserted into the hollow space ofthe frame element. Thus, the electromagnetic implementation of theapparatus such as that depicted in FIG. 21 may have the electromagneticassembly 312 constructed as the cylindrical hollow frame element, andthe magnetization-redistributing electromagnetic winding assembly 311constructed as the cylindrical rotor element. Both elements may besupported with the their respective symmetric longitudinal axiscoinciding each other, and the rotor element is positioned inside thehollow space of the frame element such that both the rotor and the frameare rotatable with respect to the coinciding axes and to each other.This configurational arrangement is one that is preferred for thoseapparatuses of the invention employing mechanical rotary commutator.

On the other hand, it is also possible to construct an apparatus withthe structural configuration that is reversed with respect to that ofFIG. 21. In such a configurational arrangement, themagnetization-redistributing electromagnetic winding assembly 311 isconstructed as the cylindrical hollow frame element, and theelectromagnetic assembly 312 is constructed as the cylindrical rotorelement. In other words, the frame element becomes the one that iscommutated by the rotary commutator. This may be an arrangement suitablefor the electromagnetic implementations of the invention employing thepower electronics rotary commutators.

Although the invention has been described in considerable detail withreference to certain preferred versions thereof, other versions arepossible. For example, in the electromagnetic implementation of theapparatus of the invention, the electric machine utilized as theelectromagnetic power-transmitting device may adopt the pan-cakestructural configuration, in which interaction between the twoelectromagnetic elements takes place among the disk surfaces rather thanthe cylindrical periphery as is in the hollow cylindrical arrangement.Further, for the mechanical implementation of the power transmissionapparatus adopting the parallel-axis configuration, a fixed-ratiocoupling may be used to replace the variable-speed power-transmittingmeans that is integrated with the epicyclic gear train. When the gearratio of this fixed-ratio coupling is selected to be close to point C onthe driven element speed line 103 of FIGS. 5-7 and 8-10, the resultantpower transmission apparatus becomes a large-reduction-ratio gear train.Such a large-reduction fixed-ratio gear drive is simple to construct andis able to handle large power. Therefore, the spirit and scope of theappended claims should not be limited to the description of thepreferred versions contained herein.

What is claimed is:
 1. A power transmission apparatus for transmittingpower, the apparatus having an input shaft for receiving mechanicalpower from an external power source and an output shaft for deliveringmechanical power to an external load, the power transmission apparatuscomprising:an eddy-current coupler comprising a driving element and adriven element, the eddy-current coupler is connected to the input shaftand receives the external mechanical power at an input angular speed,and the driving and the driven elements operate at a driving and adriven angular speed respectively for transmitting the mechanical powervia interaction between the driving and the driven elements, whereinsaid driving and driven angular speeds are variable with respect to eachother; and an epicyclic gear train comprising a first gear, a secondgear and a third gear, the second gear rotates in the same rotationaldirection as the third gear and at an angular speed slower than thethird gear when the third gear is driven with the first gear heldstationary, the third gear is connected to the driving element of theeddy-current coupler, the second gear is connected to the driven elementof the eddy-current coupler, and the first gear is connected to theoutput shaft; whereby the power-transmitting interaction of theeddy-current coupler operating at the driving and the driven angularspeeds is redistributed onto the output shaft by the epicyclic geartrain, and the output shaft delivers the mechanical power to theexternal load at an output angular speed.
 2. A power transmissionapparatus for transmitting power, the apparatus having an input shaftfor receiving mechanical power from an external power source and anoutput shaft for delivering mechanical power to an external load, thepower transmission apparatus comprising:a power-transmitting meanscomprising an eddy-current coupler, the eddy-current coupler comprisinga driving element and a driven element, the power-transmitting means isconnected to the input shaft and receives the external mechanical powerat an input angular speed, and the driving and the driven elementsoperate at a driving and a driven angular speed respectively fortransmitting the mechanical power via interaction between the drivingand the driven elements; and an epicyclic gear train comprising a firstgear, a second gear and a third gear, the second gear rotates in thesame rotational direction as the third gear and at an angular speedslower than the third gear when the third gear is driven with the firstgear held stationary, the third gear is connected to the driving elementof the power-transmitting means, the second gear is connected to thedriven element of the power-transmitting means, and the first gear isconnected to the output shaft; whereby the power-transmittinginteraction of the power-transmitting means operating at the driving andthe driven angular speeds is redistributed onto the output shaft by theepicyclic gear train, and the output shaft delivers the mechanical powerto the external load at an output angular speed.